原理:(1)外层div比内层div大一个像素,外层div不能有overflow:hidden样式.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
ul{ height:31px; border-bottom:1px solid #ccc; padding:0; margin:0; list-style:none}
li{ height:30px; border-bottom:2px solid #f00; float:left; margin:0px 5px; width:40px;}
</style>
</head>
<body>
<ul>
<li></li>
<li></li>
</ul>
</body>
</html>