It didn't center for me in either IE or FF - until I added the good old fashioned <CENTER> tags around the table... then it worked in both. May not be politically correct, but it works.
<h3>Find People...</h3>
<p>To start your search, please select a category from below, or use our search facility found above.</p>
<table class="front_cat_table">
<tr>
<td>
<p align="center"><img src="/image/7/793107-desk_1091.gif" alt=" desk_1091 " border="0"></td>
<td>
<p align="center"><img src="/images/793855-tn_chat_923.gif" border="0" height="32" width="32"></td>
</tr>
<tr>
<td>
<p align="center">Businesses</td>
<td>
<p align="center">People</td>
</tr>
</table></CENTER>
</DIV>
Code:
<DIV><CENTER> <h3>Find People...</h3>
<p>To start your search, please select a category from below, or use our search facility found above.</p>
<table class="front_cat_table">
<tr>
<td>
<p align="center"><img src="/image/7/793107-desk_1091.gif" alt=" desk_1091 " border="0"></td>
<td>
<p align="center"><img src="/images/793855-tn_chat_923.gif" border="0" height="32" width="32"></td>
</tr>
<tr>
<td>
<p align="center">Businesses</td>
<td>
<p align="center">People</td>
</tr>
</table></CENTER>
</DIV>
