<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.main{position:relative;padding:0 210px;}
.left{position:absolute;left:0;top:0;width:200px;height:500px;background-color:red}
.right{position:absolute;right:0;top:0;width:200px;height:500px;background-color:red}
.middle{height:500px;background-color:#000}
</style>
</head>
<body>
<div class="main">
<div class="left"></div>
<div class="middle"></div>
<div class="right"></div>
</div>
</body>
</html>
原文：https://www.cnblogs.com/zhangyongxi/p/9549238.html