pseudo-selector 伪选择器
pseudo-element selector 伪对象选择器
pseudo element selector 伪元素选择符
Pseudo-class Selector 伪类选择符
A simple selector is either a type selector or universal selector followed immediately by zero or more attribute selectors, ID selectors, or pseudo-classes, in any order.
一个简单选择符或者是一个类型选择符，或者是一个全局选择符，紧跟在后的是零个或多个属性选择符，ID选择符或伪类，次序任意。
Rules that apply the: hover pseudo-selector to non-link elements.
对非链接元素应用：hover伪选择器的规则。
After looking at this a little more, it seems the pseudo-selector of ": contains (')" is no longer within the CSS3 spec.
看这多一点之后，它似乎的伪选择“：包含(' ')”不再是CSS3规范之内。
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