<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="zh-CN">
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<style>
.header{
width: 200px;
height: 200px;
background: blue;
float: left
}
.main{
width: 200px;
height: 200px;
background: red;
float: left
}
.footer{
width: 200px;
height: 200px;
clear: left;
float: left;
background: green
}
.bootom{
width: 200px;
height: 200px;
float: left;
background: black
}
</style>
<body>
<div class="header"></div>
<div class="main"></div>
<div class="footer"></div>
<div class="bootom"></div>
</body>
</html>
原文：http://aabbc59.blog.51cto.com/3844828/1640900