CSS依赖于模式匹配规则来确定哪个样式应用于文档中的哪个元素。这些模式称为选择器，范围从标记名（例如，

pto match paragraph tags) to very complicated patterns that match very specific parts of a document. For example, p#myid > b.highlightwould match any btag with a class of highlightthat is a child of the paragraph with the id myiA CSS selector is the part of a CSS style call that identifies what part of the web page should be styled. The selector contains one or more properties that define how the selected HTML

The CSS Selectors

There are several different types of selectors:

• type selectors – matching a specific element
• class selectors – matching elements with a specific class
• ID selectors – matching the element with a specific ID
• descendant selectors – matching elements that are descendants of a specific element
• child selectors – matching elements that are a child of the specific element
• universal selectors – matching any element
• adjacent sibling selectors – matching elements immediately preceded by a specific element
• attribute selectors – matching elements with a specific attribute or attribute value
• pseudo-class selectors – matching elements with a specific pseudo-class
• pseudo-element selectors – matching elements with specific pseudo-element properties

Format CSS Styles and CSS Selectors

The format of a CSS style looks like this:

selector { style property : style ; }

Separate multiple selectors that have the same style with commas. This is called selector grouping. For example:

selector1, selector2 { style property : style ; }

Grouping selectors is a shorthand mechanism to keep your CSS styles compact. The above grouping would have the same effect as:

selector1 { style property : style ; }selector2 { style property : style ; }

Always Test Your CSS Selectors

Not all older browsers support all the CSS selectors. If you are setting up CSS for use with browsers as old as IE8 or older, be sure to test your selectors in as many browsers on as many operating systems as you think might be used to access your code. If you are using CSS1, CSS2, or CSS3 selectors for use with current browsers, you should be fine.