<!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>
<link href="style.css" rel="stylesheet" />
<style type="text/css">
#box
{
/*高度必须设置，否则IE下子元素的absolute定位异常。且此处应设置为100%，因为内容部分的高度不确定。*/
height:100%;
position:relative;
}
#middle
{
height:100px;
margin:0 200px;
background-color:red;
}
#left
{
height:100px;
200px;
position:absolute;
top:0px;
left:0px;
background-color:green;
}
#right
{
height:100px;
200px;
position:absolute;
top:0px;
right:0px;
background-color:blue;
}
</style>
</head>
<body>
<div id="box">
<!--优先加载中间部分，后加载两侧-->
<div id="middle"></div>
<div id="left"></div>
<div id="right"></div>
</div>
</body>
</html>