<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
*{margin:0;padding:0;}
.box{height:500px;background-color:#f00 ;position:relative;}
.box1{height:500px;background-color:green;margin-top:-50px;}
.a,.b{background-color:#fff;display:block;border:1px solid #000;}
.a{position:absolute;left:0;bottom:0;width:100%;height:50px;color:#fff;z-index: 1;background-color:#0000EE;}
.b{position:relative;z-index:0;height: 100px;background-color:#fff;}
</style>
</head>
<body>
<div class="box">
<a class="a" href="#">aaaa</a>
</div>
<div class="box1">
<a class="b" href="#">bbb
<br />
<br />bbb
<br />
<br />bbb <br />
</a>
</div>
</body>
</html>
父标签box和box1的z-index问题,前者z-index比后者大就不会遮挡了,ie7层级的高低不仅要看自己,还要看自己的老爸这个后台是否够硬(笑)。