Delphinidin

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.

The history of how CSS came to be isn’t actually all that relevant to CSS authors of today, so you can skip the next bit if you’re in a hurry. If, like me, you’re interested in the nitty-gritty, read on.

In the early days of the Web, nine different proposals were made to the World Wide Web Consortium, the main standards organization for the Web which is more commonly known as the W3C, for a style sheet language to help separate the visual appearance of a document from its content. In 1994, Cascading HTML Style Sheets was proposed by Håkon Wium Lie, now CTO of Opera Software (a company you’ll meet again later in this chapter), but at the time he was working at CERN with Tim Berners-Lee and Robert Cailliau, the two men who invented the World Wide Web. CHSS became CSS because CSS can be applied to more than just HTML, and in December 1996 the CSS level 1 Recommendation was published.

Since then, three more CSS specifi cations have been published by the W3C. CSS 2 became a recommendation in 1998, with CSS 2.1 (which fi xes a few mistakes in 2), and CSS 3 currently existing as candidate recommendations.

Although CSS 3 is still under development, CSS 2.1 is likely to become a fully fledged recommendation in the near future and is well supported by all modern browsers.