Yep - You need to put the full URL to that image in the following line:
HTML Code:
<td width="20" valign="top" background="images/edge/misc/left_border.gif"><img border="0" src="http://www.s2tg.com/images/edge/misc/left_border.gif" width="20" height="5"></td>
It looks like you changed the image URL itself but you missed the background one. That piece of code should be towards the top of the header template.