Might want to provide an image for everyone to help as the page requires a person ot be logged in to see it.
However i'd guess one of two things:
1.) You probably only removed the contents of the sidebar container, but not the container itself (probably a div). Thus the container is still taking up its designated space, even though it has no contents. To fix, remove the sidebar container.
2.) The container to the left of the sidebar container is a fixed width div that is aligned to the left. So even if you remove the sidebar container, the main container will still keep to its designated width and no more. To fix, increase the width of the main container, or better yet have it expand dynamically.