<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>左右固定，中间自适应</title>
<style>
html ,
body ,
div{
margin:0;
padding:0;
}
.left ,
.right {
float: left;
width:300px;
height:300px;
background:orange;
}
.right{
float: right;
}
.center{
height:300px;
background:red;
}
</style>
</head>
<body>
<div class="left">左边</div>
<div class="right">右边</div>
<div class="center">中间</div>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>左右自适应，中间固定</title>
<style>
html ,
body ,
div{
margin:0;
padding:0;
}
.left,
.right {
float: left;
margin: 0 0 0 -300px;
width: 50%;
}
.main {
width: 600px;
float: left;
background: green;
}
.inner {
padding: 20px;
}
.left .inner,
.right .inner {
margin: 0 0 0 300px;
background: orange;
}
.left,
.right {
float: left;
margin: 0 0 0 -300px;
width: 50%;
*width: 49.9%;
}
</style>
</head>
<body>
<div class="left">
<div class="inner">左边</div>
</div>
<div class="main">
<div class="inner">中间</div>
</div>
<div class="right">
<div class="inner">右边</div>
</div>
</body>
</html>
CSS 左右固定，中间自适应宽度 及 左右自适应宽度，中间固定
原文：http://www.cnblogs.com/zion0707/p/4480677.html