I would guess between your header and navbit template. It could be the $spacer_open. You can't just take that out though, but you should take a look at it and see what sort of spacing it adds.
You can find which template is putting in that space by going - vboptions > General Settings > Add Template Name in HTML Comments > set to Yes . Then go back to your page and view the source code and you will see the name of the template called around your part of the code.