<table border="1" width="100%">
<tr>
<td width="33%"> </td>
<td width="33%"> </td>
<td width="34%"> </td>
</tr>
<tr>
<td width="33%"> </td>
<td width="33%">
<iframe src="pagina_contenuta_nell'_iframe name="iframe" width="100%" height="100%"></iframe>
</td>
<td width="34%"> </td>
</tr>
<tr>
<td width="33%"> </td>
<td width="33%"> </td>
<td width="34%"> </td>
</tr>
</table>

dove sta l-errore?