Update. After searching bit on here, I think I found what I need:

<table class="t_inner" align="center" width="800">
<tr>
<td align="center" valign="middle" width="325">
<a href="http://My Forum URL/" target="_top">
<img alt="FORUM NAME" width="300" height="50"
src="YOUR_FORUM_LOGO" border="0"></a>
</td>
<td align="center" valign="middle">

<!--// This gives you another column for ads, etc //-->

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