Delphinidin

Some plants, including dodders, broomrapes, and pinedrops, have no chlorophyll (necessary for photosynthesis) and have become dependent on chlorophyll-bearing plants for their nutrition. They parasitize their host plants via peglike projections called haustoria (singular: haustorium), which develop along the stem in contact with the host.

- Contractile Roots
Some herbaceous dicots and monocots have contractile roots that pull the plant deeper into the soil. Many lily bulbs are pulled a little deeper into the soil each year as new sets of contractile roots are developed. The bulbs continue to be pulled down until an area of relatively stable temperatures is reached.

Velamen roots of orchids, prop roots of corn and banyan trees, adventitious roots of ivies, and photosynthetic roots of certain orchids are among various kinds of aerial roots produced by plants. It was formerly assumed that the epidermis of velamen roots, which is several cells thick, aided in the absorption of rain water. It appears, however, it may function more in preventing loss of moisture from the root. Corn prop roots, produced toward the base of the stems, support the plants in a high wind.

Most plants produce either a fibrous root system, a taproot system, or, more commonly, combinations of the two types. Some plants, however, have roots with modifications that adapt them for performing specific functions as well as the absorption of water and minerals in solution. Variation of specialized roots:

Water, even after air has been bubbled through it, contains less than one-thirtieth the amount of free oxygen found in the air. Accordingly, plants growing with their roots in water may not have enough oxygen available for normal respiration in their root cells. Some swamp plants, such as the black mangrove (Avicennia nitida) and the yellow water weed (Ludwigia repens), develop special spongy roots, called pneumatophores, which extend above the water’s surface and enhance gas exchange between the atmosphere and the subsurface roots to which they are connected.

- Food-Storage Roots
Most roots and stems store some food, but in certain plants, the roots are enlarged and store large quantities of starch and other carbohydrates, which may later be used for extensive growth. In sweet potatoes and yams, for example, extra cambial cells develop in parts of the xylem of branch roots and produce large numbers of parenchyma cells. As a result, the organs swell and provide storage areas for large amounts of starch and other carbohydrates. Similar foodstorage roots are found in the deadly poisonous water hemlocks, in dandelions, and in salsify. In carrots, beets, turnips, and radishes, the food-storage tissues are actually a combination of root and stem. Although the external differences are not obvious, approximately 2 centimeters (0.8 inch) at the top of an average carrot is derived from stem tissue that merges with the root tissue below.

Most of the cells mature, or differentiate, into the various distinctive cell types of the primary tissues in this region, which is sometimes called the region of differentiation, or roothair zone. The large numbers of hairlike, delicate protuberances that develop from many of the epidermal cells give the root-hair zone its name. The protuberances, called root hairs, which absorb water and minerals, adhere tightly to soil particles with the aid of microscopic fibers they produce and greatly increase the total absorptive surface of the root.

The region of elongation, which merges with the apical meristem, usually extends about 1 centimeter (0.4 inch) or less from the tip of the root. Here the cells become several times their original length and also somewhat wider. At the same time, the tiny vacuoles merge and grow until one or two large vacuoles, occupying up to 90% or more of the volume of each cell, have been formed.

Cells in the region of cell division, which is composed of an apical meristem (a tissue of actively dividing cells) in the center of the root tip, produce the surrounding root cap. Most of the cell divisions take place next to the root cap at the edges of this inverted cup-shaped zone, located a short distance behind the actual base of the meristem. Here the cells divide every 12 to 36 hours, while at the base of the meristem, they may divide only once in every 200 to 500 hours. The divisions are often rhythmic, reaching a peak once or twice each day, usually toward noon and midnight, with relatively quiescent intermediate periods. Cells in this region are mostly cubical, with relatively large, more or less centrally located nuclei and a few very small vacuoles.

Close examination of developing young roots usually reveals four regions or zones. Three of the regions are not sharply defined at their boundaries. The cells of each region gradually develop the form of those of the next region, and the extent of each region varies considerably, depending on the species involved. These regions are called:

When a seed germinates, the tiny, rootlike radicle, a part of the embryo (immature plantlet) within it, grows out and develops into the first root. The radicle may develop into a thick, tapered taproot, from which thinner branch roots arise, or many adventitious roots may arise from the stem, which is attached to the radicle and continuous with it. Adventitious roots are those that do not develop from another root but develop instead from a stem or leaf. A fibrous root system, which may have large numbers of fine roots of similar diameter, then develops from the adventitious roots. Many mature plants have a combination of taproot and fibrous root systems.

All cells secrete certain substances that can damage the cytoplasm, if allowed to accumulate internally. Such materials either must be isolated from the cytoplasm of the cells in which they originate or moved outside of the plant body.

In woody plants, the epidermis is sloughed off and replaced by a periderm after the cork cambium begins producing new tissues that increase the girth of the stem or root. The periderm constitutes the outer bark and is primarily composed of somewhat rectangular and boxlike cork cells, which are dead at maturity.

Most of the tissues we have discussed thus far consist of one kind of cell, but a few important tissues are always composed of two or more kinds of cells and are sometimes referred to as complex tissues. Two of the most important complex tissues in plants, xylem and phloem, function primarily in the transport of water, ions, and soluble food (sugars) throughout the plant. Some complex tissues are produced by apical meristems, but most complex tissues in woody plants are produced by the vascular cambium and are often referred to as vascular tissues.

The outermost layer of cells of all young plant organs is called the epidermis. Since it is in direct contact with the environment, it is subject to modification by the environment and often includes several different kinds of cells. The epidermis is usually one cell thick, but a few plants produce aerial roots called velamen roots (e.g., orchids) in which the epidermis may be several cells thick, with the outer cells functioning something like a sponge. Such a multiple-layered epidermis also occurs in the leaves of some tropical figs and members of the Pepper Family (Piperaceae), where it protects a plant from desiccation.

Phloem tissue, which conducts dissolved food materials (primarily sugars) produced by photosynthesis throughout the plant, is composed mostly of two types of cells without secondary walls. The relatively large, more or less cylindrical sieve tube members have narrower, more tapered companion cells closely associated with them.

Xylem tissue is an important component of the “plumbing” and storage systems of a plant and is the chief conducting tissue throughout all organs for water and minerals absorbed by the roots. Xylem consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells. Vessels are long tubes composed of individual cells called vessel elements that are open at each end. As each vessel element develops, the perforation plate, in some instances, can become barlike strips of wall material that extend across the openings. However, the flow of fluid through the vessels is not blocked by the strips.

- Parenchyma
Parenchyma tissue is composed of parenchyma cells, which are the most abundant of the cell types and are found in almost all major parts of higher plants. They are more or less spherical in shape when they are first produced, but when all the parenchyma cells push up against one another, their thin, pliable walls are flattened at the points of contact. As a result, parenchyma cells assume various shapes and sizes, with the majority having 14 sides. They tend to have large vacuoles and may contain starch grains, oils, tannins (tanning or dyeing substances), crystals, and various other secretions.

Unlike animals, plants have permanent regions of growth called meristems, or meristematic tissues, where cells actively divide. As new cells are produced, they typically are small, six-sided, boxlike structures, each with a proportionately large nucleus, usually near the center, and with tiny vacuoles or no vacuoles at all. As the cells mature, however, they assume many different shapes and sizes, each related to the cell’s ultimate function; the vacuoles increase in size, often occupying more than 90% of the volume of the cell.

All animals have either internal or external skeletons or skeleton-like systems to support their tissues. Animal cells do not have cell walls; instead, the plasma membrane, called the cell membrane by most zoologists (animal scientists), forms the outer boundary of animal cells. Higher plant cells have walls that are thickened and rigid to varying degrees, with a framework of cellulose fibrils. Higher plant cells also have plasmodesmata connecting the protoplasts with each other through microscopic holes in the walls.

Scientists use the scanning electron microscope (SEM) to study the details of many different types of surfaces. Unlike the light microscope or even a transmission electron microscope, which form images by passing either a beam of light or electrons through a thin slice of fixed tissue, the SEM’s great advantage is its ability to allow us to look at surfaces of specimens and observe topographical detail not possible with other types of microscopy.

The cytoskeleton is involved in movement within a cell and in a cell’s architecture. It is an intricate network constructed mainly of two kinds of fibers—microtubules and microfilaments. Microtubules control the addition of cellulose to the cell wall. They are also involved in cell division, movement of cytoplasmic organelles, controlling the movement of vesicles containing cell-wall components assembled by dictyosomes, and movement of the tiny whiplike flagella and cilia possessed by some cells.

In a mature living plant cell, as much as 90% or more of the volume may be taken up by one or two large central vacuoles that are bounded by vacuolar membranes (tonoplasts). The vacuolar membranes, which constitute the inner boundaries of the living part of the cell, are similar in structure and function to plasma membranes.

Various small bodies distributed throughout the cytoplasm tend to give it a granular appearance. Examples of such components include types of small, spherical organelles called microbodies, which contain specialized enzymes and are bounded by a single membrane. Peroxisomes, for instance, contain enzymes needed by some plants to survive during hot conditions in a process called photorespiration, whereas glyoxisomes contain enzymes that aid in the conversion of fats to carbohydrates during, for example, the germination of seeds containing fats. If present, peroxisomes are generally found associated with chloroplasts, and glyoxisomes usually are located near mitochondria.

Mitochondria (singular: mitochondrion) are often referred to as the powerhouses of the cell, for it is within them that energy is released from organic molecules by the process of cellular respiration. This energy is needed to keep the individual cells and the plant functioning as a whole. Carbon skeletons and fatty acid chains are also rearranged within mitochondria, allowing for the building of a wide variety of organic molecules. Mitochondria are numerous and tiny, typically measuring from 1 to 3 or more micrometers in length and having a width of roughly onehalf micrometer; they are barely visible with light microscopes.

Most living plant cells have several kinds of plastids, with the chloroplasts being the most conspicuous. They occur in a variety of shapes and sizes, such as the beautiful corkscrew-like ribbons found in cells of the green alga Spirogyra  and the bracelet-shaped chloroplasts of other green algae, such as Ulothrix. The chloroplasts of higher plants, however, tend to be shaped somewhat like two Frisbees glued together along their edges, and when they are sliced in median section, they resemble the outline of a rugby football.

Stacks of flattened discs or vesicles known as dictyosomes may be scattered throughout the cytoplasm of a cell. Dictyosomes are often bounded by branching tubules that originate from the endoplasmic reticulum, but are not directly connected to it. Five to eight dictyosomes per cell are typical, but up to 30 or more may be found in cells of simpler organisms.

Ribosomes are tiny bodies that are visible with the aid of an electron microscope. They are typically roughly ellipsoidal in shape with apparently varied and complex surfaces. Each ribosome is composed of two subunits that are composed of RNA and proteins; the subunits, upon close inspection, can be differentiated by a line or cleft toward the center. Ribosomes average only about 20 nanometers in diameter in most plant
cells. Unattached ribosomes often occur in clusters of five to 100, particularly when they are involved in linking amino acids together in the construction of the large, complex protein molecules that are a basic part of all living organisms.

The outer membrane of the nucleus is connected and continuous with the endoplasmic reticulum. The endoplasmic reticulum facilitates cellular communication and channeling of materials. Many important activities, such as the synthesis of membranes for other organelles and modification of proteins from components assembled from elsewhere within the cell, occur either on the surface of the endoplasmic reticulum or within its compartments.

The nucleus is the control center of the cell. In some ways, it functions like a combination of a computer program and a dispatcher that sends coded messages or “blueprints” originating from DNA in the nucleus with information that will ultimately be used in other parts of the cell. In other words, the DNA in the nucleus provides the original information needed to fulfill the cell’s needs. This nuclear information contributes toward growth, differentiation, and the myriad activities of the complex cell “factory.” The nucleus also stores hereditary information, which is passed from cell to cell as new cells are formed.

The outer boundary of the living part of the cell, the plasma membrane, is roughly eight-millionths of a millimeter thick. To get an idea of how incredibly thin that is, consider that it would take 12,500 such membranes neatly stacked in a pile to achieve the thickness of an ordinary piece of writing paper. Yet this delicate, semipermeable structure is of vital importance in regulating the movement of substances into and out of the cell. While the plasma membrane may inhibit movement of some substances, it can otherwise allow free movement and can even control movement of other substances into and out of the cell. As a result, the proportions and makeup of chemicals within a cell become quite different from those outside the cell. The plasma membrane is also involved in the production and assembly of cellulose for cell walls.

A novelty song of more than 50 years ago listed food items the writer said he disliked. Each verse ended with the line, “I like bananas because they have no bones!” Indeed, bananas and all plants differ from larger animals in having no bones or similar internal skeletal structures. Yet large trees support branches and leaves weighing many tons. They can do this because most plant cells have either rigid walls that provide the support afforded to animals by bones or semi-rigid walls that provide flexibility. At the same time, the walls protect delicate cell contents within. When millions of these cells function together as a tissue, their collective strength is enormous. The redwoods and Tasmanian Eucalyptus trees, which are the largest trees alive today, exceed the mass and volume of the largest land animals, the elephants, by more than a hundred times. The wood of one giant redwood tree could support the combined weight of a thousand elephants.

Most plant and animal cells are so tiny they are invisible to the unaided eye. Cells of higher plants generally vary in length between 10 and 100 micrometers.1 Remember that the resolution of a light microscope is 2 micrometers, making it useful for the study of eukaryotic cells. Since there are roughly 25,000 micrometers to the inch, it would take about 500 average-sized cells to extend across 2.54 centimeters (1 inch) of space; 30 of them could easily be placed across the head of a pin. Some prokaryotic (bacterial) cells are less than onehalf micrometer wide, while cells of the green alga, mermaid’s wineglass (Acetabularia), are mostly between 2 and 5 centimeters long, and fiber cells of some nettles are about 20 centimeters long.

Imagine the excitement of the first scientist who observed cells! This discovery was made in 1665 by the English physicist Robert Hooke, who used a primitive microscope to examine thin slices of cork found in stoppered wine bottles:

Nucleic acids are exceptionally large, complex polymers originally thought to be confined to the nuclei of cells but now known also to be associated with other cell parts. They are vital to the normal internal communication and functioning of all living cells. The two types of nucleic acids—deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Enzymes are mostly large, complex proteins that function as organic catalysts under specific conditions of pH and temperature. By breaking down bonds and allowing new bonds to form, they facilitate cellular chemical reactions, even at very low concentrations, and are absolutely essential to life. None of the 2,000 or more chemical reactions in cells can take place unless the enzyme specific for each one is present and functional in the cell in which it is produced. Enzymes increase the reaction rate as much as a billion times, and without them, the chemical reactions in cells would take place much too slowly for living organisms to exist. Enzymes are often used repeatedly and usually do not break down during the reactions they accelerate. Enzyme names normally end in -ase (e.g., maltase, sucrase, amylase).

Some plant food-storage organs, such as potato tubers and onion bulbs, store small amounts of proteins in addition to large amounts of carbohydrates. Seeds, in particular, however, usually contain proportionately larger amounts of proteins in addition to their complement of carbohydrates and are very important sources of nutrition for humans and animals.

The cells of living organisms contain from several hundred to many thousands of different kinds of proteins, which are second only to cellulose in making up the dry weight of plant cells. Each kind of organism has a unique combination of proteins that give it distinctive characteristics. There are, for example, hundreds of kinds of grasses, all of which have certain proteins in common and other proteins that make one grass different from another. The hundreds of kinds of daisies are distinguished from each other and from grasses by their particular combinations of proteins.

Lipids are fatty or oily substances that are mostly insoluble in water because they have no polarized components. They typically store about twice as much energy as similar amounts of carbohydrate and play an important role in the longer term energy reserves and structural components of cells. Like carbohydrates, lipid molecules contain carbon, hydrogen, and oxygen, but there is proportionately much less oxygen present.

Carbohydrates are the most abundant organic compounds in nature. They include sugars and starches and contain C, H, and O in a ratio of, or close to a ratio of, 1C:2H:1O (CH2O). The number of CH2O units in a carbohydrate can vary from as few as three to as many as several thousand. There are three basic kinds of carbohydrates:

The large molecules comprising the majority of cell components are called macromolecules, or polymers. Polymers are formed when two or more small units called monomers bond together. The bonding between monomers occurs when a hydrogen (H+) is removed from one monomer and a hydroxyl (OH–) is removed from another, creating an electrical attraction between them. Since the components of water (H+ and OH–) are removed (dehydration) in the formation (synthesis) of a bond, the process is referred to as dehydration synthesis. Dehydration synthesis is controlled by an enzyme.

The living substance of cells consists of cytoplasm and the structures within it. The numerous internal structures, which vary considerably in size. About 96% of cytoplasm and its included structures are composed of the elements carbon, hydrogen, oxygen, and nitrogen; 3% consists of phosphorus, potassium, and sulfur. The remaining 1% includes calcium, iron, magnesium, sodium, chlorine, copper, manganese, cobalt, zinc, and minute quantities of other elements. When a plant first absorbs these elements from the soil or atmosphere, or when it uses breakdown products within the cell, the elements are in the form of simple molecules or ions.

Energy is the ability or capacity to do work or to produce a change in motion or matter. Energy exists in several forms and is required for growth, reproduction, movement, cell or tissue damage repair, and other activities of whole organisms, cells, or molecules. On earth, the sun is the ultimate source of life energy.

The concentration of H+ ions present is used to define degrees of acidity or alkalinity on a specific scale, called the pH scale. The scale ranges from 0 to 14, with each unit representing a tenfold change in H+ concentration. Pure water has a pH of 7—the point on the scale where the number of H+ and OH– ions is exactly the same, or the neutral point.1 The lower a number is below 7, the higher the degree of acidity; conversely, the higher a number is above 7, the higher the degree of alkalinity.

Water molecules are held together by weak hydrogen bonds. In pure water, however, a few molecules sometimes dissociate into hydrogen (H+) and hydroxyl (OH–) ions, with the number of H+ ions precisely equaling the number of OH– ions.

Bonds are forces that form molecules by attracting and holding atoms together. Bonds can form in several different ways. The number of electrons in an atom’s outermost energy level determines how many chemical bonds can be formed by that particular atom. If the number of electrons in the outermost energy level is less than eight, the atom may lose, gain, or share electrons, resulting in an outermost energy level that contains the maximum number of electrons. Three types of chemical bonds are of particular significance for living organisms:

1. The Missouri Botanical Garden is one of the oldest botanical institutions in the United States. It is a center for botanical research and science education.

http://www.mobot.org

2. Australian National Botanic Gardens provides a wealth of botanical and biological information about Australia.

http://www.anbg.gov.au/anbg/

The study of plants, called botany—from three Greek words botanikos (botanical), botane (plant or herb), and boskein (to feed), and the French word botanique (botanical)—appears to have had its origins with Stone Age peoples who tried to modify their surroundings and feed themselves. At first, the interest in plants was mostly practical and centered around how plants might provide food, fibers, fuel, and medicine. Eventually, however, an intellectual interest arose.

Our dependence on green organisms to produce the oxygen in the air we breathe and to remove the carbon dioxide we give off doesn’t stop there. Plants are also the sources of products that are so much a part of human society that we largely take them for granted. We know, of course, that rice, corn, potatoes, and other vegetables are plants ; but all foods, including meat, fish, poultry, eggs, cheese, and milk, to mention just a few, owe their existence to plants. Condiments such as spices and luxuries such as perfumes are produced by plants, as are some dyes, adhesives, digestible surgical stitching fiber, food stabilizers, beverages , and emulsifiers.

It has been estimated that the total human population of the world was less than 20 million in 6000 B.C. During the next 7,750 years, it rose to 500 million; by 1850, it had doubled to 1 billion; and 70 years later, it had doubled again to 2 billion. The 4.48-billion mark was reached in 1980, and within 5 years, it had grown to 4.89 billion. It is presently increasing by nearly 80 million annually, and estimates for the year 2006 are over 6.5 billion. By 2025 it is believed the world’s population will exceed 7.8 billion. The earth remains constant in size, but humans obviously have occupied a great deal more of it over the past few centuries or at least have greatly increased in density of population.

You Tube can be a great way to market your product or business. However, there is more to You Tube than simply uploading your video and hoping that people will watch it. You have to market your marketing video as well! The following is a list of 10 tips that will help you if you are using You Tube for marketing purposes.

If you are considering using You Tube to market your business, product, or services then the first thing you need to do is to create and customize your own channel. This isn't really as difficult as it sounds. In fact, although it is very important, the website itself does most of the work for you.

When you are signing up for a You Tube account in order to market your business, services, or products, one of the most important things you can do is to choose the right niche. Why? Because it can help you with marketing purposes even within You Tube.

So now you have created a marketing video for your business or product and you have uploaded it to You Tube. What do you do next? The next important thing is choosing your tags and categories for your video.

The tags and categories might be more important than you think. It could even be that in the past you just skipped over that part and didn't choose any at all. However, in order to help promote your video, and to get people to find it once it's on the website, you need to choose ones that are relevant.

Did you know that every week You Tube either puts out new features that will help you enhance your videos or improves upon features that already exist? This is great news when it comes to marketing your videos, especially if you use You Tube in order to promote your own business.

If you do a random search on the internet right now for viral marketing tips, you will find scores of websites with information available for you to peruse. Why? Because it is a hot topic these days. It's no wonder, either.

Viral marketing can be used in many different ways, from videos to even e-books. If you are trying to promote your own business and you want to create a top-notch video for marketing purposes then you really cant go wrong with viral marketing. Viral videos are most one of the utilized forms of marketing today.

Many business owners are creating perfect You Tube marketing videos and using them to promote their website, business, or products. It's a great way to get some recognition, as well as to drive traffic to your website. When you combine social networking sites, you pick up traffic that you might not have ordinarily received on your traditional website.

So what is a niche targeted playlist and how can it help you with your You Tube marketing video?

Making a playlist is actually a very simple thing to do. This article will read as though you are using your own videos, as opposed to gathering together other user's videos. After all, if you want to market your own products or business then it would presumably be your videos that will point your audience to your external website.

Your You Tube marketing video doesn't just have to contain information about your product or services. In fact, there are scores of different things that you can do with your video to make it the perfect marketing video.

You Tube can be a great place to upload your marketing video for your business or product. Millions of people get on You Tube everyday to watch videos and ours can be one those that people watch. If you include your website address and other information then hopefully people will then be driven to your website and purchase something.

You Tube can be a powerful marketing tool for your business or products that you are trying to promote. Most of the You Tube videos are shot by amateurs and are low-budget. That doesn't mean that a lot of work didn't go into them, however. Still, the videos are mostly done on a low budget.

When it comes to uploading your videos onto You Tube for marketing purposes, there are actually three categories of videos that they can fit into. These three categories of videos are thekind that generate traffic, which is essentially what you want when it comes to posting your videos on You Tube to begin with-especially if they are meant to market your new product or business.

Do you want your You Tube marketing video to be seen? Are you running out of ideas as to how to market it for little to no money? Well, one of the best ways that you can promote your perfect marketing video is to join the community.
Once you have uploaded your video, chosen your categories and video tags, and let it settle into the website, you can't just sit back and hope that traffic comes to it-you must market it as well.

You can use YouTube to market your business, product, or services. However, you need a good video in order to draw traffic and make people want to visit your website after they have finished watching.

qTip is a jQuery plug-in that allows you to easily set up advanced tooltips on any element. The tooltips can contain both static and dynamic content. qTip has many features that make it an extremely attractive and lightweight plug-in such as cross-browser compatibility with IE, Firefox, Safari, Opera, and Chrome. On those browsers that aren't supported, the tooltip degrades gracefully. qTip can be applied to any element on the page, including paragraph tags.

If you have ever purchased something online, you probably had to fill out a form by entering your billing address and shipping address. For most consumers, this information is the same, so such forms often have a Same As Billing Address check box that says “same as billing" that copies over all the form fields from billing to shipping, preventing the customer from needing to re-enter all of that information. This check box uses a copy field functionality. Not only does it save the customer time, but also reduces the likelihood of them mis-entering data. An example of a copy field check box on the checkout page of Best Buy's Web site (www.bestbuy.com).

E-mail validation is critical for a newsletter sign-up on a Web site. If users submit a bad e-mail address, it can cost you time and money to get it cleaned out your database. Using jQuery, you can set up simple e-mail validation on a form without having to write a lot of code. This sort of script can be useful on a Web site, such as the Laithwaites Wine special off er email sign-up form, where you don't need to validate multiple fields with different types data requiring advanced validation. I demonstrate advanced validation using a popular jQuery validation plug-in at the end of this chapter. It's important to remember that you should never rely solely on client-side JavaScript validation; server-side validation should always be present if client-side is not available.

Using jQuery to retrieve the value from a select option is also simple to set up, yet can be very useful in any type of Web site or application. An example of this functionality can be seen on Crutchfield.com, a car and home audio electronics Web site, in the Outfit Your Car section. Crutchfield allows you to select your car year, model, and make — each time you make a selection, the value of the select option a retrieved and then used to display another option with list items that are filtered by the previous select.

Retrieving the value of an input is a very basic form technique and is useful in many situations. It's incredibly easy to set up and can be used for a number of applications. I commonly use this technique when submitting forms using Ajax when I need to pass over the values from all of the form fields.

You can use jQuery to programmatically select and deselect all of the check boxes on a Web page, a technique that is often used with a preferences section on a Web site. The user sees 20 or so check boxes and a link that lets them select all of the check boxes with a single click. The following tutorial shows you how you can set up a Check All Check Boxes link using the jQuery click event and conditional logic.

Being able to limit a character count on an input field can be used to restrict how many words are included or how many characters you can include in your status message. The 140-character limit on Twitter (www.twitter.com) has made the limiting character count type of script quite popular in the past year, but it's still always a challenge to keep your message or thought under 140 characters. A character count limit can also display to the user how many characters they have left to work with under the limit.

Setting default text on form fields helps to instruct users on what needs to be entered into the fields. Many Web designers use the default text as form input labels to help save space or change up the design of the forms. You can set a default value using the value attribute, but the problem is that if a user clicks into the field, they need to delete what is currently there. The Laithwaites Wine Web site (www.laithwaiteswine.com) has a simple implementation of this: their e-mail newsletter signup field at the bottom left corner of the Web page.

In larger forms, you can help users keep track of where they are by highlighting which field they are currently on. Most browsers have built-in events that highlight the current field, such as the Firefox. You can set up a secondary highlight using CSS and the jQuery focus event. By adding a custom highlight, you can ensure that users know how far along they are in any given form. Using CSS, you can add a highlight as shown on the contact form example from Wufoo (www.wufoo.com).

Forms are commonplace all over the Internet, whether they are forms for ecommerce and registration or search input fields. Validation ensures that Web forms accept correct data, show clear error messages when faulty data is entered, and that fields are filled out when a form is submitted. Validation is often handled on the server side by Web developers using programming languages such as PHP, JSP or ASP. Validation on the client side using JavaScript is becoming increasingly more common, in addition to server-side validation depending on the security level of the data that is being validated. Web designers who know jQuery and JavaScript can create a better user interface with forms than can a developer using backend development. jQuery offers several events (focus, blur, change) specifically to be used in forms, which I review in post before, about events. These events are not new to JavaScript, but jQuery makes it easier to use these events in conjunction with forms. In this chapter, I review many different scenarios where jQuery can help you do more with your forms. The techniques that you learn from this chapter are necessary when you work with Ajax.

Interactive graphs are most often creating using Adobe Flash for dynamic graphs, such as those seen in Google Analytics. Recently, a number of developers have created jQuery plug-ins that can create comparable charts but without the dependency of Flash. The Visualize plug-in, created by Filament Group, is one of the better solutions for creating charts. The Visualize plug-in allows you to create graph, line, bar, and pie charts using tabular data. It has a number of options that can be passed into the function to set up and alter a chart on any page using data pulled from HTML tables.

jQuery has an extensive community of developers who create jQuery plug-ins. The only downside to having so many options to choose from is that sometimes the quality of code and support for a plug-in is lacking. You can usually tell a good plug-in from a bad one by the documentation that accompanies it. You can build your own jQuery code to do table sorting and filtering, but quite a few powerful plug-ins can also do this. Using a plug-in can rapidly speed the implementation of a solution, and because most plug-ins are open source, it gives you a good base to get started upon. I review how to work with two plug-ins in particular: tablesorter and Visualize.

Pagination involves breaking up content into manageable page-sized pieces. On the Web, pagination is everywhere; like pagination on the Google search results page. Pagination helps to limit the number of results shown at one time to make it easier for users to navigate and digest the content delivered to them.

- Adding a Row After a Row Based on Its Index Value
Just as you add a row based on its position in the table as first or last, you can also insert a row based on the index value of the row proceeding or following it. Set up a selector that selects all elements that have an index of 5 using the :eq() filter and insert the Special Offer TODAY HTML content directly after the matched element.

Now that you have seen how to add simple styling and effects to tables, I’m going to show you how to manipulate the data that is in the tables. When I say manipulate, I mean add, remove, and filter the data contained, which results in changes to the DOM. All of the selectors, events, and effects that I have discussed up until now can be applied to tabular data. The possibilities of what you can do are endless. In this section, I explain the following solutions:

In the late nineties, during the explosive growth of the Internet and the World Wide Web, tables were oft en used for page design and layouts, which is not what they were originally intended for. The problem with using tables for design and layout stems from their lack of support for semantic principles, where content is separated from design, and the usage of nested tables, which add unnecessary page bloat to your code and lead to an accessibility and maintainability nightmare. Nested tables occur when you create a page layout with table upon table nested into each other to match up to a complex design. Most Web designers and developers are now able to work purely with HTML and CSS to create semantic designs that no longer use tables for layout and therefore separate the content from the presentation layers. HTML tables were used improperly because alternative layout options did not exist until the advent of CSS — even then, browsers didn't support CSS correctly for quite a few years. Tables have a really bad reputation, but if they're used correctly for tabular data, they can be quite useful for showing data in a clean, structured format. In the following chapter, I share some ways to enhance your tabular data using jQuery.

- Adding Alternating Row Colors Using Filters
Zebra striping is a common practice used by Web designers to make table rows easier to read by adding a background color to each even or odd row, an example of zebra striping from the Web site for Performable (www.performable.com). Zebra striping can be done using backend programming languages such as PHP or ASP.net, but the downside is that a developer must be involved. The :even and :odd filters in jQuery make it incredibly easy to add this styling to any table. Set up a document ready function and, within it, add two statements to select the odd and even rows using filters. The first statement selects all of the even rows and applies the CSS property background:#dedede (light gray). The second statement is just to ensure that all of the odd rows have a background of white.

Users must always know where they are within a Web site and where they are visually on the navigation menu. This basic user interface requirement can be overlooked and often is. I have seen few solutions in jQuery or JavaScript for this issue — most solutions often involve backend programming using PHP, JSP, or ASP. The following tutorial guides you through how to set up active menu items on your Web site's navigation menu using jQuery. The jQuery script is set up to determine the selected element in the menu based on the address in the URL.

One of the more attractive features of jQuery is being able to select many elements at once and change some part of the selected elements. You may run into a situation on a page where you need to quickly change all of the hyperlinks to open in a new window, but you don't have access to the source code. The code is being generated dynamically in a PHP, JSP (Java Server Pages), or ASP (Active Server Pages) file somewhere and you can't access it.

The jQuery Easing plug-in provided by GSGD (http://gsgd.co.uk/sandbox/ jquery/easing/) allows you to add 30 diff erent types of easing effects to your Web site. The animate method already has two easing effects — swing and liner, but they're very limited — to be able to create more realistic easing effects such as bounce and elastic effects, it's best to use a plug-in. Easing controls an animation by accelerating or decelerating the rate at which it falls into place, commonly seen as an animation snapping into place. Easing gives animation a more realistic effect.

By now, you should be pretty familiar with the concept of chaining in jQuery. Chaining allows you to add multiple methods to the same statement. This helps to keep your amount of code smaller and increases the performance of your scripts. In the following example, I use chaining to illustrate how you can add multiple methods to a selector statement. The tooltip is first set to hidden, and then the element is faded in at a speed of 900 milliseconds. A one-second delay occurs, and then it fades out at a rate of 900 milliseconds.

Because animations are usually a series of events occurring within a given timeframe, being able to delay elements to create a timed animation is a basic requirement. jQuery offers a way to add delay to an animation with the delay method.
The delay method was added recently to version 1.4 of the jQuery library to allow you to add a delay to the methods that follow it, which are attached by chaining. The delay method is only to be used with effects in the jQuery library. If you are looking for a more flexible timer function, give the native JavaScript setTimeout function a shot. If you are looking to display a message to your users and have it disappear after a certain amount of time, the delay effect is the perfect solution. In this example, I want to display a message when the user hovers their mouse pointer over a link. If the user's mouse leaves the link, after 10 seconds, I want the message to fade out.

The fade-in and fade-out effects can add another dimension of interactivity to the elements on a Web site. Most oft en, the fade effect is used with image galleries or image slideshows where one image fades out as another image fades in. Up until a few years ago, it seemed the only way to achieve such an effect was by using Flash to create an animated image slideshow or by using advanced JavaScript that required many lines of code.

Searching is an integral part of the Web and quite possibly why Google is the most successful company around today. Every user expects to be able to search and easily find what they are looking for on your site. Building a better user interface that gives your users the ability to find everything your site off ers right at their fingertips is an important improvement. Mozilla has a large community of developers who create add-ons for the Firefox browser. An example of their search bar with advanced options. If you click the advanced options, the advanced option search bar slides down, which is a nice touch because it keeps you on the same page but allows you to expand your search. This feature can be easily added with jQuery using the slideToggle method. The slideToggle method is very similar to the toggle method for showing and hiding elements, except that it isn't already attached to a click event. If the element is already shown and slideToggle is invoked, it is set to slideUp. The opposite happens if the element is hidden.

The sliding effect can be seen in many places across the Web, most often with image galleries where images slide in and out of view. In addition, with the recent flux of real-time conversation brought on by Facebook and Twitter, sliding in and out of recent activity on a page is more common too. Twitter has integrated a sliding-in effect for its home page when new tweets are posted. As each new tweet is posted, the tweet slides down from the top, pushing the tweets currently on the page down, one by one, until the tweet makes its way off the page and out of visibility. The slideDown and slideUp methods are set up in exactly the same manner as are the show and hide methods. By adding the method to the selector, you can pass in two optional parameters (duration and callback). The names of the methods often can be confusing to jQuery newbies. These slideDown method makes elements visible and the slideUp method makes elements hidden.

You may encounter a situation where you need to toggle between the show effect and the hide effect. jQuery has a nice solution to that called toggle(). The toggle() method binds an event handler to the click event and lets you toggle between show and hide, based on what the current visibility of the element. The important part of the following example is to set the recipe element to hidden using CSS; the toggle works based off of that property.

Suppose you are in a situation where you may want to display a special offer or special message to your users, but you only want to show them the message once. I've often seen messages like this on Basecamp, a Web-based project management tool, when a login message is displayed telling me about some new feature. You can use the show method coupled with a return function that drops a cookie on your user's computer to prevent them from seeing this message again on the same computer, under that user account.

Showing and hiding elements using jQuery is a basic effect. I showed examples of this effect being used in previous chapters, but usually these effects can be seen used in conjunction with the click event. It is commonly used across the Internet. Google Gmail uses the show/hide effect to show the new Call Phone feature overlay.

As Web designers and front-end developers, it’s our job to make the user interface for a Web site usable. Oft en that involves moving elements on and off the screen in order to fit more content on one page. Users want and expect instant gratification: They don’t want to wait around for clunky Web sites that have many, many pages and take forever to load. Facebook, the most popular social network, with more than 500 million users, has a very interactive and fun interface driven by JavaScript. If you log in to your Facebook page, you can chat with friends and check your friend feed without having to request a new page. This user experience is created using JavaScript eff ects such as show/hide and animations. Web sites like Facebook are setting the bar high for what users are expecting from an online experience. Geolocation-based applications are starting to gain more popularity. Many of these Web sites incorporate front-end JavaScript Google Maps-type technologies. jQuery provides basic effects, such as showing, hiding, sliding, and fading. Data below outlines the basic effects that are all set up in a similar fashion and have the same optional parameters that can be passed into the methods.

Attributes of a tag are useful for passing extra information about the tag, or for interacting with JavaScript. A common HTML tag is the <a> anchor tag, which can have such attributes as href, rel, id, class, title, href lang. Selecting by attribute works well with form fields because you can search inputs by name, type, attribute, class, ID, and so on.

Learning how to use selectors to navigate the DOM is the first step to successfully understanding jQuery. But after you have selected an element, you need to do something with it, which in this case is adding, removing, cloning, replacing, or adding styling. In the future, I refer to the selected element as the matched set because I can assume that selector has returned an element.

CSS and jQuery feel like they are meant to work together. I often wonder how I survived so long without using jQuery, especially when working so extensively with CSS. Up until this point, I have been using the .css() method to add CSS properties to HTML elements on the page in most of my examples. Th e downside to using the .css() method is that it adds inline styles to the HTML. If you would prefer to keep the code cleaner, I would suggest adding and removing classes instead.

Is very similar to working with CSS in HTML. The events are separated from the elements that they are being attached to. In native JavaScript, all of the events are embedded directly into the HTML, which makes it a chore to maintain any custom events and makes it easy to screw something up. You have all of these functions in an external file, but they are added to the elements as inline JavaScript, so if something changes in one element, it has to be updated in all of the elements. With jQuery, all of the element selection and event handling is done outside of the DOM in a JavaScript file.

- Filtering Elements That Do Not Contain Any Elements or Text
Finding empty elements in the DOM can be useful. If you have an empty element on your page, you can use the :empty filter to find it. In the following HTML example, I want to hide the error div if it is empty. I just need to select the .error class and add the :empty filter. If the error message has content, it remains showing; otherwise, the display:none CSS is applied to it.

Filtering allows you to refine the elements that you are selecting. Filters are very handy when you're trying to target just one, or a few, elements within your DOM. If you have a static HTML document, it is easy to adjust the HTML. But in cases where the DOM changes with every page request or load, you need to use a dynamic front-end language such as JavaScript to add formatting on the fly. A filter is defined by a colon that follows the actual filter: :filter. As of jQuery 1.7.1, jQuery contains many different filters. I give real-world examples of the most common.

- Selecting Page Elements by Using Parent-Child Selectors
Parent-child selectors are a useful way to select elements within your page, when tag, CSS, and ID elements cannot be used. The parent-child CSS property is available in CSS to all popular browsers except IE6. Are you surprised? I'm not, but the beauty of using this CSS selector with jQuery is that IE6 is supported. The parent-child selector can be very useful when working with nested elements such as navigation menus.

Variables are a great way to store types of information, especially when writing JavaScript.  Using variables when writing jQuery is no diff erent than using them with JavaScript. You can set variables and call them within the jQuery wrapper because it's all basically just JavaScript. The beauty of jQuery is that it is JavaScript, so if you have any prior knowledge of JavaScript, you can directly apply that knowledge to jQuery. You don't have to worry about learning new syntax, conventions, or methods because most of jQuery is based on JavaScript functionality, but the syntax is much easier to understand.

Selectors, an essential feature of the jQuery library, are powered by the jQuery Sizzle selector engine. Sizzle can be used with other languages, but its real power is best used with all the other jQuery methods. The syntax is easy to understand for Web designers who have a solid understanding of CSS and HTML. The jQuery Sizzle selector engine is JavaScript code written to handle selectors in jQuery. The selectors are common CSS and XPATH selectors with the addition of a few custom selectors.

JavaScript has native functions that can select elements by ID and tag. The downside of these functions is that you have to use a diff erent function for each of the three types of elements. Also, this creates repetition and code bloat, which can become a nightmare to manage. When you use selectors in jQuery, one selector can handle multiple types of elements. This makes writing clean and manageable code much easier.

Before you get started programming with jQuery, you need to understand what the jQuery wrapper is and how it applies to the DOM. A wrapper, in most programming languages, is something that wraps something else to extend the functionality, most often an object. To put this in perspective, the jQuery wrapper attaches itself to the DOM by using selectors and allows you to extend the DOM. jQuery doesn't actually off er any new methods; it just takes methods that already exist in native JavaScript and makes them much easier to interact with.

After you have decided which approach you want to take — either downloading a library or using a hosted version of jQuery — you need to set it up in your Web page. The jQuery library can be included within script tags and live in between the <head></head> tags of your HTML document, or you can include the jQuery library before your closing </body> tag. You must include any CSS (cascading style sheets) before the jQuery library and jQuery custom code because you want to ensure that all CSS is applied to the DOM (Document Object Model) before you try to change it with jQuery.

Most jQuery-specific code needs to be set up within a document.ready() event handler method. But native JavaScript such as variables, arrays, and so on can be set up outside of the document ready event handler because they don't need to wait for the DOM to be ready and are hidden from the DOM as they are specifics within the actual script.

Conflicts can occur with other JavaScript libraries if you don't take the proper precautions when writing your jQuery. Most conflicts occur with the use of the $ alias, which Prototype also shares as an alias. You need to take two steps to eliminate conflicts with others libraries:

- Cross-Browser Compatibility
With the recent updates to Safari, Firefox, Internet Explorer, Google Chrome, and Opera, creating pages that work across all of the major browsers is the top priority. Browser wars have become a part of every Web designer's daily struggle.

Web sites have become much more than just text, images, and links to other pages. Internet users expect greatness from a Web site and the bar is constantly being raised by Web sites and companies such as Facebook, Google, Microsoft , Twitter, and Foursquare, to name a few. The technology is constantly changing, and using jQuery helps you keep up with the fast pace. jQuery is a library that promotes rapid development of Web sites or applications and allows you to focus on user interaction and interface design without having to write long, bloated code.

When you select a framework, you have about 20 JavaScript libraries to choose from, with five of those libraries being the main players. These five main players — YUI, Prototype, MooTools, Dojo, and the topic of this book, jQuery — have risen up above the rest because of their ease of use and the enormous audiences they have. The main differentiators between most of these libraries include size and browser support.

jQuery was created in 2006 by John Resig as an alternative to more complicated JavaScript libraries. jQuery enables Web designers and developers to write simpler JavaScript that still enables them to perform advanced JavaScript functions on their Web sites.

The <table> element has several optional elements that can be used to enhance the presentation and semantic value of a table, including captions, columns, headings, and footers. Take a look at a <table> element that makes use of all these optional elements. When I get into the discussion of styling tables, beginning with the section “Table Captions,” you’ll need to understand what is possible in a table.

The position property is used to give elements different types of positioning. Positioning gives you the ability to dictate with precision where in a document you want an element to appear. You can choose whether an element appears relative to a container element, or relative to the browser window. You can layer elements one on top of another. The following code outlines the position property and its values, and the four offset properties, top, right, bottom, and left, and their possible values.

Whats new in Lines 3.1?

+ [Updated] Skins code for latest SVN Version (398)
+ [Improved] Font size
+ [Improved] Transload progress bar style
+ [Improved] Server files style
+ [Misc] Logo changed & renamed from logo_pm.gif to webcloud_logo.png
+ [Misc] Stylesheet renamed from rl_style_pm.css to webcloud_style.css
+ [Removed] Index.html in "images" folder (folder already protected by .htaccess)

Whats new in Lines 3.1 ?

+ [Updated] Skins code for latest SVN Version (398)
+ [Improved] Font size
+ [Improved] Transload progress bar style
+ [Misc] Logo changed & renamed from logo_pm.gif to lines_logo.png
+ [Misc] Stylesheet renamed from rl_style_pm.css to lines_style.css
+ [Removed] Index.html in "images" folder (folder already protected by .htaccess)

Lists are a very versatile group of elements in HTML, used for all sort of things, such as site and page navigation, tab controls, and simple lists of items such as for tasks or shopping basket contents. Lists consist of two parts. The first is the list container element, which is either <ul> for lists without any particular order or <ol> for lists that have a specifi c order to the items within it, and in which the order matters.

- Vertically Aligning Content
The vertical-align property is used primarily in two contexts. In one context, it is used to vertically align text appearing within the lines of a paragraph. One example of this creates subscript or superscript text. The vertical-align property may also be used to align the content appearing inside a table cell. The following code outlines the vertical-align property and its possible values.

- Floating Content
A simple explanation of the float property is that it is used to put content side-by-side. In the coming sections, you look in depth at the float property, its idiosyncrasies, and how you can use it to lay out a web page. The following code outlines the float property and its values.

- Padding
Padding is the space between the content of an element and its borders, as has been mentioned briefly in previous examples. The following code shows the various padding properties.

- Line Height
The line-height property refers to the height of the line on which each line of text appears. The line-height property and its values are outlined in the following code.

- Background Colors
The background-color property is used to specify a solid background color. The following code shows the possible values for the background-color property.

The CSS box model is a collection of properties that define the amount of space around an element, its dimensions, its margins, its borders, and padding between the content of the element and the borders. Around the outside of an element is space called the margin, inside of the margin is the border, inside of the border is the padding, and inside of the padding is the content of the element. In the coming sections, I pick apart the various properties that comprise the box model in CSS, beginning with margin.

ITALIC, BOLD, SMALL CAPS

- Italic Text
The font-style property is used to switch between styles provided by a particular font; those styles are italic or oblique. For many fonts the information required to render text in an italic version of the font is included in the font file. The oblique style does not use this information, even if it is available, instead it simulates italicized text, not always to great effect. The following table outlines the possible values for the font-style property.

Whats new in svn 399 ?

[SECURITY] Fix xss vulnerability in note.php - Th3-822
[PLUGIN] Added/fix download & upload plugin - Th3-822, vdhdevil, Ruud v.Tony, carlton, rezasalami, defport, pasolvon, Dreamsky, simpledescharga n all rapidleech forum member who want to spend their time to contribute for the rapidleech script development.

The font-family property allows you to specify the typeface used to display a piece of text. You can specify more than one typeface, and the first one that the user has installed on their system will be the one used. You can make use of any of the fonts installed on the user’s operating system, though in practice you’ll generally stick to the set of web safe fonts that we discuss later. There are also some so-called generic font families that browsers map to the most appropriate system font, as in the following code.

The available font families that can be specified vary depending on the operating system. Using a default installation, Windows does not provide the same fonts as Mac OS X, for instance. Furthermore, the available fonts also vary depending on the programs installed on the user’s computer. For instance, Microsoft Office installs a number of extra fonts in addition to those that ship with Mac OS X or Windows. In fact, with the exception of a few fonts, Mac OS X with Microsoft Offi ce installed provides pretty much the same fonts as installed on Windows. Without Microsoft Office installed, however, many Windows fonts are not available on the Mac platform.

Along with the need for the cascade in CSS is the need to override it. This is where !important rules come in. The !important syntax appears within a declaration, after the property value and before the semicolon that terminates the declaration. Two components make up this syntax: an exclamation mark, used here as a delimiter; and the important keyword. A delimiter marks the ending of one thing and the beginning of another. Here the exclamation mark signals the end of the declaration. The important keyword must appear next, followed by a semicolon to terminate the declaration; this is demonstrated in the following code.

CSS Selectors - Part 2

- The Universal Selector
The universal selector is an asterisk. When used alone, the universal selector tells the CSS interpreter to apply the CSS rule to all elements in the document. The following code shows what a universal selector looks like.

* {font-family: Arial, Helvetica,sans-serif;}

This rule is applied to all elements contained in the document. The universal selector applies to everything, including form input fi elds and tables of data. It applies style to any and every element present in a document. In this case all elements would have font-family: Arial, Helvetica,sans-serif;
applied to them. You probably won’t use the universal selector very often because, there are better ways of applying styles to the whole document.

- Descendant Selectors
In CSS, descendant means an element that is a child, grandchild, great grandchild, and so on, of another element. Descendant selectors apply style based on whether one element contains another.
Descendant selectors are used to select an element based on its context within the document. In the preceding code, you select a <h2> element but only if the <h2> element is a descendant of the <div> element with a class of planet. Descendant selectors aren’t limited to just two elements; you can include more elements in the ancestral lineage, if it suits your needs. Each selector in a descendant selector chain must be separated by a space. This is demonstrated in the following code.

div.planet table td {padding: 0 10px 0 0;text-align: left;}

In fact, the entire lineage from the eldest ancestor, the <html> element, down through the generations to the element you want to select, can be included in a descendant selector chain.

- Pseudo-Classes
Pseudo-classes are used to represent dynamic events, a change in state, or a more general condition present in the document that is not easily accomplished through other means. This may be the user’s mouse rolling over or clicking on an element. In more general terms, pseudo-classes style a specific state present in the target element, for example, a previously visited hyperlink. Pseudo-classes allow the author the freedom to dictate how the element should appear under different conditions. There are many more pseudo-classes than are listed here. Unlike normal classes, pseudo-classes have a single colon before the pseudo-class property.

-- Dynamic Pseudo-Classes
The following are considered dynamic pseudo-classes. They are a classifi cation of elements only present after certain user actions have or have not occurred:
+ :link: Signifies unvisited hyperlinks
+ :visited: Indicates visited hyperlinks
+ :hover: Signifies an element that currently has the user’s mouse pointer hovering over it
+ :focus: Signifies an element that currently has focus, for example if the user has used their keyboard to navigate to a link
+ :active: Signifies an element on which the user is currently clicking

If you want to apply styles to an anchor regardless of its state you can, of course, still use the good old type selector without a pseudo class.

--# :link and :visited
The :link pseudo-class refers to an unvisited hyperlink, whereas :visited, of course, refers to visited hyperlinks. These two pseudo-classes are used to separate styles based on user actions. An unvisited hyperlink may be blue, whereas a visited hyperlink may be purple. Those are the default styles your browser applies. Using dynamic pseudo-classes it is possible to customize those styles. In the following code, unvisited links are styled with the :link dynamic pseudo-class. They receive medium blue text. Visited links, on the other hand, have magenta text.

There is one exception to this, however. Webkit browsers will apply :link pseudo class styles to all links, not just unvisited ones. Therefore it is a good idea to defi ne the same properties in :link and :visited rules so that the correct styles are applied.For obvious reasons, the :link and :visited pseudo-classes apply only to <a> elements.

The order in which dynamic pseudo-classes appear in the style sheet is important and has to do with the cascade. If the :link pseudo-class is defi ned after the :focus pseudo-class in the style sheet, the :link pseudo-class takes precedence: The declarations with the :link pseudo-class override those defi ned for the :focus pseudo-class.

--# :hover and :focus
The :hover pseudo-class refers to an element over which the user’s mouse pointer is currently hovering. While the user’s mouse pointer is over the element, the specifi ed style is applied; when the user’s mouse pointer leaves the element, it returns to the previously specifi ed style. The :focus pseudo-class behaves in the same way, but for keyboard focus. To provide the same experience to keyboard and mouse users, it is good practice to include them both and is common for them to receive the same style.

The :hover and :focus pseudo-classes are applied in the same way that the :link and :visited pseudo-classes are applied. I like to put :focus fi rst as it stops me forgetting it. An example appears in the following code. When the user either hovers over the <a> element with their mouse or uses the keyboard to navigate to it, this code causes the text within the <a> element to be underlined.

In IE 6, the :hover pseudo-class applies only to hyperlinks (which is incorrect under the CSS 2 specification), whereas other browsers recognize the :hover pseudo-class on any rendered element, per the CSS 2 specifi cation. This problem is fixed in IE 7 and later.

--# :active
The :active pseudo-class refers to an element that the user is currently clicking and holding down the mouse button on. The specifi ed style remains in place while the user holds down the mouse button, and the element does not return to its original state until the user releases the mouse button. The following code shows the :active pseudo-class in use. When the user clicks an <a> element, while the mouse button is held down, and before it is released, the element is said to be active, in which case the styles in the :active pseudo-class rule are applied. In IE 6 and IE 7, :active applies only to hyperlinks; whereas, other browsers allow it to be applied to any element.

Read Again :
CSS Selectors - Part 1

CLASS AND ID SELECTORS
Class and ID selectors are the most widely supported. In fact, they are as widely supported as the type selector. There are two types of selectors. The class selector, which references the class attribute used on HTML elements, is the more generic of the two, meaning it may encompass many elements in a given document, even elements of different types or purposes. On the other hand, you can use the id attribute on only one element in an HTML document, so we use it in CSS to reference an element that is unique
per page. Besides using it in CSS, you can also use an element’s class or ID to access it via a scripting language such as JavaScript. You can also link to the location of the element with an ID name using fragment identifiers. Anchors are appended to URLs to force a browser to go to a specifi c place in a document. You can think of the id attribute as an element’s address inside a document: No two addresses can be the same.

CSS is very flexible regarding how you call it in a document. You can include CSS in a document in four ways:

- CSS can be included in a document by using embedded style sheets, which are included between <style> and </style> tags directly in an HTML document. These tags must appear between the <head> and </head> tags.

CSS has a number of options for specifying colors, ranging from a 216-color, Web-safe palette to the full range of colors available in the RGB format, a total of 16,777,216 colors! More specifically, those options are as follows:

There are two kinds of lengths used in CSS: relative and absolute. Absolute lengths are not dependent on any other measurement. An absolute measurement retains its length regardless of the environment (operating system, browser, or screen resolution of a computer monitor) in which it is applied. Relative lengths, on the other hand, depend on the environment in which they’re used, such as the computer monitor’s screen resolution or the size of a font.

As i know, you cannot install different versions of Internet Explorer on the same
copy of Windows. For development, you need a way to test IE 6, IE 7, IE 8, IE 9, and IE 10 since you’ll
have visitors to your website on all five browsers. The following are a few ways to do this:

Unlike with many traditional programming languages on the Web, we don’t get to choose the environment in which CSS and HTML is run; your end users make this decision by selecting which web browser they use. Although CSS is a standard supported by all major browsers, there are often differences between them, so it is important to be aware of the top players and to be able to test in each of them before releasing professional code. It is worth taking a look at Yahoo!’s Graded Browser Support page at http://developer.yahoo.com/yui/articles/gbs/, which is regularly updated to show the current range of browsers that Yahoo! recommends that developers test in. It is based on traffi c analysis to the Yahoo! network and is quite representative of the Internet as a whole.

To write CSS, just as is the case when writing HTML source, you will need a text editor. Word processing programs such as Microsoft Word aren’t ideally suited for CSS, because they automatically do lots of things that are helpful when writing a letter or book, such as correct spelling but get in the way when writing code. Instead, you want something that doesn’t make any changes that you don’t want to what you type but lets you write and save plain text.

By using CSS for the presentation of a document, you can substantially reduce the amount of time you spend composing not only a single document but an entire website As you’ll discover, CSS is much more versatile than the styling mechanisms provided by HTML alone. The versatility of CSS, when harnessed effectively, can reduce the amount of hard disk space that a website occupies, as well as the amount of bandwidth required to transmit that website from the server to the browser. CSS has the following advantages:

Cascading Style Sheets (CSS) is a language designed for describing the appearance of documents written in a markup language such as HTML. With CSS you can control the color of text, the style of fonts, the spacing between paragraphs, how columns are sized and laid out, what background images or colors are used, and a variety of other visual effects. One of the major benefi ts is that the same CSS can be used by more than one page, meaning that the style of an entire website can be adjusted without having to change each page individually. The most common use for CSS is to style web pages, and in combination with HTML or XHTML (which is used to describe content) and JavaScript (which is used to add interactivity to a site), CSS is a very powerful tool.