Question : div content transparent in firefox

http://www.partnerspa.com.au/div.htm
How can I prevent text content of the 'behind' div from showing in FireFox
It doesn't show in IE

<div style="border:1px solid #000; background-color:#CCCCCC; height:50px; width:50px">
this<br/>
is<br/>
behind
</div>
<div style="border:1px solid #000; background-color: #FFFFCC; text-align:right; height:200px; width:200px; margin-top:-40px">
front
</div>

Answer : div content transparent in firefox

Here's one way:

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<div style="border:1px solid #000; background-color:#CCCCCC; height:50px; width:50px;">
this<br/>
is<br/>
behind
</div>
<div style="position:relative; top:-30px; left:3px; border:1px solid #000; background-color: #FFFFCC; text-align:right; height:200px; width:200px;">
front
</div>