I have a list of banners that I want to reside in the middle of my site, here is the code:

Code HTML4Strict:
<div id="banner-ads">
<ul>
<li><a href="#">Banner Ad 1</a></li>
<li><a href="#">Banner Ad 2</a></li>
<li><a href="#">Banner Ad 3</a></li>
<li><a href="#">Banner Ad 4</a></li>
</ul>
<p><a href="#">Advertise here!</a></p>
</div>

My site is liquid, but I can't figure out the way to get the <div> container to always keep the list centered.

Thanks for any pointers!