CSS: The Definitive Guide, 5th Edition

Chapter 1. CSS Fundamentals

Cascading Style Sheets (CSS), a powerful programming language that transforms the presentation of a document or a collection of documents, has spread to nearly every corner of the web as well as many ostensibly nonweb environments. For example, embedded-device displays often use CSS to style their user interfaces, 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 (JS) frameworks and even in JS 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 NCSA Mosaic, for example, permitted the user to define each element’s font family, size, and color. 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 dozen other element types. If a user configured their browser to make all level-one headings tiny and pink and all level-six headings huge and red, well, that was their lookout.

It was into this milieu that CSS was introduced. Its goal was to provide a simple, declarative styling language that was flexible for web page authors and, most importantly, provided styling power to authors and users alike. By means of the cascade, these ...