Chapter 17. Selectors

The selector is the part of the style rule that identifies the element (or elements) to which the presentation instructions are applied. For instance, if you want all of the h1s in a document to be green, write a single style rule with h1 as the selector. But that's just the beginning. CSS provides a variety of selector types to improve flexibility and efficiency in style sheet authoring. This chapter introduces the selectors included in the CSS 2.1 specification, including:

• Type (element) selectors

• Contextual selectors (descendant, child, and adjacent sibling)

• Class and ID selectors

• Attribute selectors

• Pseudoclasses

• Pseudoelements

Not all of these forward-thinking selectors are supported by today's browsers, so if a particular selector is not quite ready for prime time, it will be noted.

The W3C Selectors specification introduces additional selectors above and beyond those in CSS 2.1, which modern browsers are still in the process of implementing. This book does not describe them. For more information on those new selectors in particular, see the W3C Selectors specification (www.w3.org/TR/css3-selectors).