在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head>
<style>[class|=top]
{
background:yellow;
}
</style>
</head>

<body>
<h1 class="top-header">Welcome</h1>
<p class="top-text">Hello world!</p>
<p class="content">Are you learning CSS?</p>

<p><b>Note:</b> For [<i>attribute</i>|=<i>value</i>] to work in IE8 and earlier, a DOCTYPE must be declared.</p>

</body>
</html>

源代码

动行结果