CSS规则的结构和Grouping、class和id
作者 佚名技术
来源 CSS技术
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发布时间 2012-03-04
2.1 规则的结构
<rules>::=<selector>
<左括号><declarations><右括号>
<declarations>::=
<declaration>{<SEMICOLON><declaration>}[SEMICO
LON]
<SEMICOLON>::=分号
<declaration>::=<property><COLON>
<value>
<COLON>::=冒号
<value>::=<keyword list>
<keyword list>::=<keyword>{<SPACE><keyword>}
<SPACE>::=空格
通常会用空格做为value之间的分隔符，有个例外：
As we''ve seen, CSS keywords are separated by spaces—except in one instance. In the CSS property font, there is exactly one place where a forward-slash (/) can be used to separate two specific keywords. Here''s an example:
h2 {font: large/150% sans-serif;}
The slash separates the keywords that set the element''s font size and line height. This is the only place the slash is allowed to appear in the font declaration. All of the other keywords allowed for font are separated by spaces.
2.1.1 selector
selector: defines which piece of the document will be affected.
Selector通常是html元素，也可能是xml中允许任何元素。
2.1.2 Declarations and Keywords
2．2 Grouping
2.2.1 grouping selectors
将多个元素共用一个style，例子：
/* group 1 */h1 {color: silver; background: white;} h2 {color: silver; background: gray;} h3 {color: white; background: gray;} h4 {color: silver; background: white;} b {color: gray; background: white;} /* group 2 */ h1, h2, h4 {color: silver;} h2, h3 {background: gray;} h1, h4, b {background: white;} h3 {color: white;} b {color: gray;} /* group 3 */ h1, h4 {color: silver; background: white;} h2 {color: silver;} h3 {color: white;} h2, h3 {background: gray;} b {color: gray; background: white;} 2.2.1.1 The universal selector * {color: red;} 2.2.2 grouping declarations 例子： h1 {font: 18px Hel |
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