An IE crash bug

<style type="text/css">
#ab{margin:0 25px;position:relative;border:1px solid;
font:bold;text-decoration:none;list-style:none;}
a:hover{display:block;color:#000;width:50px;}
#cd{display:none;}
a:hover #cd{
display:block;background:#edecdc;
border:1px solid #f3f3f8;
padding:10px 20px;color:#009933;
}
</style>
<a href="" title="" id="ab">
Try moving here!
<span id="cd">Here is the prompt information!</span>
<span id="cd">Here is the prompt information!</span>
</a>
<a href="" title="" id="ab">
Try moving here!
<span id="cd">Here is the prompt information!</span>
<span id="cd">Here is the prompt information!</span>
</a>
<!--
1. The menu should be wrapped in <a></a>, because IE6 only supports a:hover effect
2. a:hover to open display:block:
3. Selectors should be related to each other, such as: a#cd:hover span{}
4. Use table
-->