If you need different column width, do this:
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td colspan="9">
<table>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
</table>
</td>
</tr>