The way you did it makes a total of four columns:
HTML Code:
<tr>
<td colspan="3" width="426" height="147" valign="top"><table width="100" border="0" cellpadding="0" cellspacing="0">
<!--DWLayoutTable-->
<tr>
<td width="426" height="147" valign="top"><img src="images/2e_forest/2EVOLVE_forest_01.png" width="426" height="147"></td>
<td align="$stylevar[right]" id="header_right_cell">
<td align="right">
$random_banner[1]
</td>
</tr>
</table></td>
</tr>
You do have the top column width set to 426 and then the first column in the table also set to 426. That makes no sense. I'm not sure why you do that or what sort of affect that is going to have here. Why are you doing that? You may want to rethink the html for your table.