manual side solumn not working on showthread template

[rockon]

I'm adding a right column to pages that would be difficult to do custom with CMPS integration, e.g. showthread, and it won't work on my showthread template :S

This is what I've done:

Immediately below '$navbar':

<table cellpadding="0" cellspacing="0" style="margin: 0px; padding: 0px; width: 100%;">
   <tr>
      <td valign="top">

Directly in-between '$similarthreads' and '$footer':

      </td>
      <td width="200px" valign="top" style="padding-left: 8px;">

         <div style="padding-bottom:8px;"> 
	    <table align="center" border="0" cellpadding="3" cellspacing="1" class="tborder" width="100%">
	       <thead> 
		   <tr> 
		      <td class="tcat" colspan="4"> 
 
                         <table cellpadding="0" cellspacing="0">
                            <tr>
                               <td>  
                                  <span class="smallfont"><strong>Advertisement</strong></span> 
                               </td>
                            </tr>
                         </table> 
 
                      </td> 
		   </tr> 
		</thead> 
	        <tbody>
                   <tr>
                      <td>
                          Content
                      </td>
                   </tr>
                </tbody>
             </table>
          </div>

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

The page to see what it shows is:

http://www.rockonpublishing.co.uk/showthread.php?t=12

Any ideas why it's not working? It works on other pages e.g.:

http://www.rockonpublishing.co.uk/contactus.php?

--------------- Added [DATE]1264268262[/DATE] at [TIME]1264268262[/TIME] ---------------

Spelling error in title and...

For your aid, the table at the bottom of the showthread page saying "Advertisement" is what is meant to be in a cell to the right.