wow. that does look pretty messed up.
Just looking at the html for the footer section I see some incorrect table nesting. Let me show you:</tr>
<tr>
<table border=0 width="95%" align="center" cellpadding="4" cellspacing="0">
<tr>
<td align="right"><font face="Arial" size="1">
<a href="http://forum.snitz.com"><acronym title="Powered By: Snitz Forums 2000 Version 3.1 SR4">Snitz Forums 2000</acronym></a>
</font></td>
</tr>
</table>
</font>
</td>
</tr>
</table>
The code in blue is what I believe would be from the inc_footer.asp file you modified. Now if you look closely, the footer table is starting in a TR. It should be an opening <TD> tag before it. I don't know where else there might be nesting errors but you just need to go over the html code and check for them. The only extra table tags in the forum that would have caused trouble would have been in the inc_footer.asp file, but you modified the file that it only contains one table now, correct?
One way of finding out where the problem lies is starting from the furthest table and setting the table border to 1, and look to see which table is not lining up right.