网页（1-3-1）动态布局
左右中间的部分宽度分别为20% 50% 20%. 网页布局呈现出1-3-1的动态布局
<!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>1-3-1动态布局</title>
<style type="text/css">
#header,#content,#footer{
background-color:#ccc;
border:1px solid #0ca;
height:30px;
width:80%;
margin:10px auto;
}
#content{
height:500px;}
#content1{
height:500px;
width:50%;
background-color:#C90;
float:left;}
#left{
height:500px;
width:30%;
float:left;
background-color:#CC0;}
#right{
width:20%;
height:500px;
float:right;
background-color:#F90;
}
</style>
</head>
<body>
<div id="header"></div>
<div id="content">
<div id="left"></div>
<div id="content1"></div>
<div id="right"></div>
</div>
<div id="footer"></div>
</body>
</html>
