说明：把鼠标移上去试试吧！
效果： aaaaaaaaa
代码：
<body>
<style>
a:link {text-decoration: none;}
a:visited {text-decoration: none;}
a:active {text-decoration: none;}
a:hover {text-decoration:underline;padding-bottom:8px;border-bottom:1 solid black}
</style>
<a href="#">把鼠标移上来！</a>
</body>