<table border="1" width="300" height="302">
<tr>
<td height="302" width="300" valign="bottom"> ---- вот и будет тебе выравнивание по низу

<table border="1" width="100" height="166">
<tr>
<td valign="bottom" height="166" width="100">&nbsp;</td>
</tr>
</table>

</td>
</tr>
</table>