Web Design in a Nutshell, 3rd Edition

Rule Syntax

Style sheets consist of one or more rules for describing how a page element should be displayed. The following example contains two rules. The first rule makes all the h1s in a document gray; the second specifies that paragraphs should be set in 12-pixel high Verdana or some sans-serif font:

    h1 {color: #eee;}
    p {font-size: 12px;
       font-family: Verdana, sans-serif; }

Figure 16-1 shows the components of a style sheet rule.

The two main sections of a style sheet rule are the selector (which identifies the element to be styled) and the declaration (the style or display instructions to be applied to that element). In the previous sample code, the h1 and p elements are the selectors. The complete list of selectors in the CSS 2.1 specification is covered in Chapter 17.

CSS History and Standards Development

HTML was never intended to be a presentational language, so the idea of using separate style sheets with HTML documents (in the manner style sheets were used in desktop publishing) has been around since 1990 when the Web was just a twinkle in Tim Berners-Lee’s eye. As early as 1993, before the release of the Mosaic browser, there were already several HTML style sheet proposals in circulation.

Cascading Style Sheets as we know them got their start in 1994 when Håkon Lie published his first draft of Cascading HTML Style Sheets. He was quickly joined by Bert Bos, who had been working with a similar style sheet system for his Argo browser. What set their style sheet proposal apart was ...