ho seguito la guida nel link e ho scritto cosi il codice
// Show the member's signature?
if (!empty($message['member']['signature']) && empty($options['show_no_signatures']))
echo '
<hr width="100%" size="1" class="hrcolor" />
<div class="signature">', $message['member']['signature'], '</div>';
echo '
</td>
</tr>
</table>
</td></tr>
</table>
</td></tr>';
if ($message['id'] == $context['first_message'])
echo'
<div align="center">
<script type="text/javascript"><!--
google_ad_client = "pub-0000000000";
/* 728x90, creato 05/01/11 */
google_ad_slot = "00000000";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript"
src="http pagead2.googlesyndication.com/pagead/show_ads.js">
</script> </div>
';
}