按: 在网上找了段代码, 作了点改动.
<html>
<head>
<style type="text/css">
u.corner u
{
height: 1px;
font-size:1px;
display: block;
overflow: hidden;
text-decoration: none;
background-color: #E0E9EB;
}
u.corner u.h1{margin: 0 5px; background-color:#9A9A9A; }
u.corner u.h2{margin: 0 3px; background-color:#EBEBEB;}
u.corner u.h3{margin: 0 2px; }
u.corner u.h4{margin: 0 1px; height: 2px; }
</style>
<head>
<body>
<div style="position: absolute; width: 90%; left:5%; top:50px; margin-bottom:10px">
<u class="corner">
<u class="h1"></u>
<u class="h2"></u>
<u class="h3"></u>
<u class="h4"></u>
</u>
<div style="background-color: #E0E9EB; height: 300px;">content</div>
<u class="corner">
<u class="h4"></u>
<u class="h3"></u>
<u class="h2"></u>
<u class="h1"></u>
</u>
<br>
</div>
</body>
</html>