I am using a 3rd party template, and I wanted to modify

Hi, I am using a 3rd party template, and I wanted to modify the menu placement. I went ahead and did so in a Template file I called Common which works fine. However if any other template is used, or the image details page is accessed the menu is messed up. I am looking for guidance on how I can make every page use the Template I called Common.

Working Page: http://www.handsonadvertising.com/advertisers/barware-ads/
Non-Working Page: http://www.handsonadvertising.com/?attachment_id=289

Note how the black menu bar under the green header works fine in the first case but fails in the second.