CSS布局：三栏布局，中间栏固定宽度，左右两边自适应
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>CSS</title>
<style type="text/css">
body{padding:0;margin:0;}
div{
height:100%;
}
#mid {
z-index:2;
background-color:#eee;
width:500px;
margin-left:-250px;
position:absolute;
top:0;
left:50%;
}
#left,#right {
z-index:1;
position:absolute;
top:0;
width:50%;
}
#left {
left:0;
}
#left .container {
margin-right:250px;
background-color:#bbb;
}
#right {
right:0;
}
#right .container {
margin-left:250px;
background-color:#bbb;
}
</style>
</head>
<body>
<div id="mid">
mid 宽度固定 : 500px
</div>
<div id="left">
<div class="container">
left 宽度自适应
</div>
</div>
<div id="right">
<div class="container">
right 宽度自适应
</div>
</div>
</body>
</html>