CSS: The Definitive Guide, 4th Edition

Chapter 1. CSS and Documents

Cascading Style Sheets (CSS) is a powerful tool that transforms the presentation of a document or a collection of documents, and it has spread to nearly every corner of the web and into many ostensibly non-web environments. For example, Gecko-based browsers use CSS to affect the presentation of the browser chrome itself, many RSS clients let you apply CSS to feeds and feed entries, and some instant message clients use CSS to format chat windows. Aspects of CSS can be found in the syntax used by JavaScript frameworks, and even in JavaScript itself. It’s everywhere!

A Brief History of (Web) Style

CSS was first proposed in 1994, just as the web was beginning to really catch on. At the time, browsers gave all sorts of styling power to the user—the presentation preferences in Mosaic, for example, permitted all manner of font family, size, and color to be defined by the user on a per-element basis. None of this was available to document authors; all they could do was mark a piece of content as a paragraph, as a heading of some level, as preformatted text, or one of a handful of other element types. If a user configured his browser to make all level-one headings tiny and pink and all level-six headings huge and red, well, that was his lookout.

It was into this milieu that CSS was introduced. Its goal was to provide a simple, declarative styling language that was flexible for authors and, most importantly, provided styling power to authors and users alike. ...