I just viewed your site as a guest, what you need to do is remove
HTML Code:
<td align="$stylevar[right]" id="header_right_cell">
<if condition="$ad_location['ad_header_logo']">$ad_location[ad_header_logo]<else /> </if>
</td>
As you aren't using that ad location you can comment it out like this
HTML Code:
<!-- <td align="$stylevar[right]" id="header_right_cell">
<if condition="$ad_location['ad_header_logo']">$ad_location[ad_header_logo]<else /> </if>
</td> -->