布局成功了！
<!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>混合布局编程挑战</title>
<style type="text/css">
body{ margin:0; padding:0; font-size:30px;color:#fff}
.top{height:50px;background-color:#666666;}
.main{background-color:red;position:relative;}
.left{background-color:blue;width:200px;height:500px;position:absolute;left:0px;top:0px; }
.right{background-color:green;height:500px;position:relative;left:220px;}
.foot{height:70px;background-color:yellow;}
</style>
</head>
<body>
<div class="top">top</div>
<div class="main">
<div class="right">right</div>
<div class="left">left</div>
</div>
<div class="foot">foot</div>
</body>
</html>
