This would get a single Iframe on oneside and two on the other:

<table border="1">
<tr>
<th rowspan="2"><iframe
src ="/default.asp">
</iframe></th>
<td><iframe
src ="/default.asp">
</iframe></td>
</tr>
<tr>
<td><iframe
src ="/default.asp">
</iframe></td>
</tr>
</table>