<html >
<head>
<title> new document </title>
<meta name="generator" content="editplus" />
<meta name="author" content="" />
<meta name="keywords" content="" />
<meta name="description" content="" />
</head>
<body>
<style type="text/css">
/*所有主流浏览器都支持 :after 伪元素。*/
.clearfix:after{content:".";display:block;height:0;clear:both;visibility:hidden}
.clearfix{*+height:1%;}/*不知道有什么用处，不加ie7也没有问题*/
.box{ background:#111;width:500px; position:relative;}
.l{float:left; background:#333;width:200px; height:100px;}
.r{float:right;background:#666;width:200px; height:200px;}
.s{width:100px; height:100px;background:#999;position:absolute;right:-50px;;}
</style>
<div class="box clearfix">
<div class="l">left</div>
<div class="r">right</div>
<div class="s">absolute</div>
</div>
</body>
</html>
