Is there a way to center the entire page on a div layout?

First off you would have to remove all absolute positioning.

Then add text-align: center; to the body section of your CSS.
[For a simple header, single div below it]
To each div add margin: auto;. If you want to change the distance it's spaced from the top of the page/div above, add margin-top: ##px; as well.
[For a header with multiple divs below it]
Add margin: auto; to the header. Create a new div that will contain all your other divs like this:
#wrap { margin: auto; width: ##px; } (change width to combined width of your divs)
Add float: left; to the div on the left and float: right; to the div on the right.
Put your two divs inside the wrap div, so it looks like
<div id="wrap">
<div id="left">
the left div
</div>
<div id="right">
the right div
</div>
</div>

Hopefully that makes sense, tried to explain it the best I could...

Thanks! :)