Thanks, Jason. That was exactly right! Thanks for the tip.
However, when I redid the editable regions in the template (see code below) the template appears fine but all the previously developed webpages look like the one attached as an example. Can you tell me why the 'main content' region is now offset to the right and how to correct it?
Obviously, the css menu and image should no longer be in the 'Main Content' region, and the left border of that region should be adjacent to the right side of the 'Sidebar' editable region.
Thanks for any help you can provide.