​x
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<style type="text/css">
a:after
{content: " (" attr(href) ")"
}
</style>
</head>
​
<body>
<p><a href="https://www.w3school.org.cn">W3School</a> contains free tutorials and references.</p>
<p><b>注释：</b>如果已规定 !DOCTYPE，那么 Internet Explorer 8 （以及更高版本）支持 content 属性。</p>
</body>
</html>
​