Listing 4 shows the CSS code for the: after pseudo-class technique.

清单4显示了：after伪类技术所使用的CSS代码。

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You can add a pressed button state with CSS by styling the active pseudo-class of the link in question.

你可以通过配置CSS中链接的active伪类来添加一个按下的按钮状态。

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A pseudo-class always consists of a "colon" (:) followed by the name of the pseudo-class and optionally by a value between parentheses.

开头，冒号后面是伪类的名称和包含在圆括号中的可选参数。

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