If you're working on a DNN skin that requires the search button to be next to the search input you're going to be annoyed by a tiny little gap that likes to insert itself between your elements.
Fear not, though, it's a relatively simple issue to fix!
The file you need to edit is:
Inside that file on line 6 you'll find a sneaky little non-breaking space element. Delete that element.
Save that file and upload it if necessary and you'll notice your search bar goes from: