Mr. Strauss.
Why two tables? I would use only one. A table the whole width and height of the page with a single cell. Everything inside the cell can be centered horizontally and vertically using traditional parameters or styles.
My example:
<style type="text/css">
body, html{height: 100%; width: 100%;}
</style>
<table style="width: 100%; height: 100%;">
<tr>
<td style="text-align: center; vertical-align: middle;">abc...</td>
</tr>
</table>
Matrix, now you have two options, use the one suits you better.
REGARDS!