Using div as a transparent button

[Cudabean]

This code works fine, but it's not quite what I want:

<div  
style="position: absolute; 
       height: 200px; 
	   width: 200px; 
	   top: 100px; 
	   left: 100px;
	   background: pink;"
onMouseOver="this.style.border='thin outset'; alert('in');"
onMouseOut="this.style.border='none';">

</div>

What I want is to be able to remove the background: pink; so that the div lets the background show through so that I've got a transparent button whose outline is apparent on rollover. However, when I remove it, it stops working completely--even the alert stops happening. I tried setting background: transparent; and the same thing happens.

I'm using IE 5.5.

cudabean