App下載
實(shí)例代碼( Tip: 登錄后體驗(yàn)更佳 )
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>W3Cschool教程(w3cschool.cn)</title> 
<style>
    h1:before {content:url(/statics/images/course/smiley.gif);}
</style>
</head>
<body>
    <h1>这是一个标题</h1>
    <p>这是一个标题：before伪元素在元素之前插入内容。</p>
    <h1>这是一个标题</h1>
    <p><b>注意:</b>仅当 !DOCTYPE 已经声明 IE8 支持这个内容属性</p>
</body>
</html>
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