<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>左右布局（左侧定宽，右侧自适应宽）</title>
<style type="text/css">
body{font:12px arial;color:#000;background:#fff;margin:0}
#header{height:50px;color:#fff;background:#666;line-height:50px;margin-bottom:10px}
#content{width:100%;color:#fff;float:right;margin-left:-240px}
#content_inner{height:400px;background:#666;margin-left:240px}
#side{width:230px;height:400px;color:#fff;background:#666;float:left}
#footer{height:50px;color:#fff;background:#666;margin-top:10px}
.clear{clear:both}
</style>
</head>
<body>
<div id="header">顶部</div>
<div id="side">左侧</div>
<div id="content">
<div id="content_inner">右侧</div>
</div>
<div class="clear"></div>
<div id="footer">底部</div>
</body>
</html>
原文：http://www.cnblogs.com/viewcozy/p/4821975.html