中间宽度自适应，两边宽度不变。当浏览器窗口缩小时中间宽度自适应缩小。自己研究了一下。弄了个。还好。浏览器也都兼容。
下面是代码：
<!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=gb2312" />
<title>布丁足迹</title>
<style>
/* www.ddhbb.com */
body{margin:0px;padding:0px;font-size:12px; line-height:1.8;font-family: Verdana,宋体;}
#wrap{ background:#0F0; height:200PX;}
#divInfo{width:100%;background:#00f; float:left;}
#sadBarA{float:left;width:200px;background:#CC9966; }
#sadBarB{margin:0 200px;background:#666;}
#sadBarC{ margin-left:-200px; float:left; background:#CC6666; width:200px; }
</style>
</head>
<body>
<div id="wrap">
<div id="divAll">
<div id="divInfo">
<div id="sadBarA">一栏</div>
<div id="sadBarB">二栏</div>
</div>
<div id="sadBarC">三栏</div>
</div>
</div>
</body>
</html>