What is CSS?

CSS is an acronym for Cascading Style Sheets. CSS is a language used to define the layout and appearance of webpages. The primary purpose of Cascading Style Sheets is to separate the content of a webpage from its layout, therefore facilitating an easy method of adapting the pages' content to the device on which it is displayed. As it is much more flexible than a table, CSS is a natural companion to XHTML in defining the appearance of modern webpages. In fact, its use is highly prioritized in more development communities and the use of tables in now considered almost taboo, even for some forms of tabular data.

Cascading Style Sheets have their roots in SGML dating back to the mid-1970's. Not surprisingly, this is the same root HTML and XHTML, the languages in which webpages are built. At the time the style sheets had no formal name, but they were nonetheless important in defining the display and layout of SGML documents of the era. When the style sheets were first adapted to HTML in the mid 1990's, the term Cascading was added, resulting in the acronym CSS. This is because the electronic versions allowed style data to be enclosed in more than one single sheet. Subsequent sheets would inherit the properties of sheets above them, and thus were termed Cascading. Another addition to the traditional style sheet was the inclusion of inline styling: predefined styles could be partially overridden on a case by case basis. For instance, if the default font, size, and colour of a body of text is predefined, and the author of the document specified that a particular word should be bold, then the colour and the size of the text is cascaded from the default predefinition automatically.

CSS is considered a web standard as it is developed and maintained by the W3C. Like HTML, CSS has different version numbers, called levels. CSS1 was the first version of the standard, published at the end of 1996. It mostly specified methods for defining markup that was otherwise possible in HTML, such as text fonts, colour, and size, as well as basic object positioning and identification. Most of the popular web browsers of the time supported CSS1 to an extent, with the notable exception of Internet Explorer. Thus, webmasters were forced to use other markup methods, such as tables, because of Internet Explorer's growing popularity. When CSS2 debuted in mid 1998, webmasters were unable to take advantage of the new tools afforded to them as their old websites were incompatible with the new features, unless they were to be completely rewritten. As IE's CSS support was still poor, few choose to do so. Those who did were forced to use hacks to work around IE's "quirks" while maintaining valid code, a feat that only professional webmasters could master. This scenario is often mentioned by anti-Microsoft activists as an example of how Microsoft prevents innovation, and is bolstered by the fact that the recent IE7 still does not comply with many basic CSS attributes.