番外3

div{text-align:center;font-size:2em;margin:20px auto;}

a{display:table;margin:0 auto;text-decoration: none;font-size:0.5em;color:#000;}

</style>

<div>404 Not Found</div>

<hr>

<a href="/">5秒钟后返回首页</a>

</body>

</html>