The problem is:
I have a full width bar menu, which is made by creating a big margin on the right and to the left. This margin should be cropped by overflow-x:
overflow-x:
How about setting the width on the content body, and warping the #container around the #menu_bar and #content_body?
#container
#menu_bar
#content_body
body div#container div#menu_bar (absolute positioned) div#links div#full_bar div#content_body (relative positioned + padding [#menu_bar height]) ...
CSS example.