CSS

HTML is the most popular document format on the Web, and it is used in most of the examples in this book.

As we explained in The Web and HTML, HTML elements enable Web-page designers to mark up a document's structure. The HTML specification lists guidelines on how browsers should display these elements. For example, you can be reasonably sure that the contents of a strong element will be displayed as boldfaced. Also, you can pretty much trust that most browsers will display the content of an h1 element using a big font size – at least bigger than the p element and bigger than the h2 element. But beyond trust and hope, you don't have any control over your text's appearance.

CSS specifications

Cascading Style Sheets is formally described in three W3C specifications: CSS1, CSS2, and CSS 2.1. (As discussed in the previous chapter, W3C is the organization that coordinates the technical development of the Web.) The first specification, CSS1, was issued in December 1996 and describes a simple style sheet language mostly for screen-based presentations. CSS1 has around 50 properties (for example, color and font-size). CSS2 was finalized in May 1998 and builds on CSS1. CSS2 includes all CSS1 properties and adds around 70 of its own, such as properties to describe aural presentations and page breaks.

CSS 2.1 is the most recent specification published by W3C. It adds some new features, but CSS 2.1 is mostly a scaled-down version of CSS2. CSS2 was an ambitious attempt to describe functionality, which Web authors had requested. However, not all the functionality is reliably supported by all browsers. CSS 2.1 is a specification that describes the parts that are supported by two or more browsers. Because CSS 2.1 is similar to CSS2, the specification was given a minor version number (that is, 2.1) rather than a major number (such as CSS3).

<%= import('ch02/rules_and_css.html.erb')%>

CSS

CSS specifications

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