Hold on Cowboy
This blog post is pretty old. Be careful with the information you find in here. The Times They Are A-Changin'
We all know that IE is full of bugs and just plain sucks as a browser… if you didn’t know that you can drop your geek badge off on the way out. So today I ran across the Z-Index bug in IE7.
Sometimes you’ve seen this behavior before: 
The fix is to give the parent of the element with a z-index a slightly higher z-index
<div style="z-index: 1000;">
<div style="z-index: 999;">Content Here</div>
</div>
Resources: http://brenelz.com/blog/squish-the-internet-explorer-z-index-bug/