How do I get a nav div to be at the very bottom and center of the header div?

Glenn

Member
I have a header div that has a height of 150px and a nav div that has a height of 15px. How do I get the nav div to float all the way to the bottom and center of the header div?
 

leroy30

New Member
<div id="header" style="width:960px;height:150px;position:relative;">
<center><div id="menu" style="width:500px;position:absolute;bottom:0;"></div></center>
</div>

??
 
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