was posted in "Development wanted" dont play the monkey :P
Now that it was moved I can answer.
one of the ways to center a div using pixels, it must be absolute positioned INSIDE a relative positioned element with a fixed width.
<style>
.a{position:relative;width:800px;margin:0 auto;background:#dddddd}
.b{position:absolute;top:300px;left:300px;width:200px;background:#fefefe}
</style>
<div class=a>
<div class=b>
This is centered
</div>
</div>
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you can center (or position anywhere you want it) editing the .b class "top" and "left" attributes