鼠标放上去显示div浮动层的大图

<style type="text/css">
<!--
.list{position:relative;}
.list span img{border-width: 0; padding: 2px; width:237px; height:176px;}
.list span{ position: absolute; padding: 3px; border: 1px solid gray; visibility: hidden; background-color:#FFFFFF; }
.list:hover{ background-color:transparent; }
.list:hover span{ visibility: visible; top:-30px; left:-34px; }
-->
</style>
<div>
<a class="list" href="#"><img src="http://www. style="padding:3px; border:#CCCCCC 1px solid" border="0" />
<span>
<img src="http://www. alt="" />
</span>
</a>
</div>