Firefox has a separate field for search queries that is in the nav bar like the location field (terminology? I mean where the URL goes) is (and like the back button, the refresh button, the "downloads" button, etc, are) but is not combined with the location field.

At least my Firefox does, and I don't think I customized that particular aspect of Firefox.

I seem to recall someone here saying that Firefox decided not to combine them (location and search fields) for privacy reasons. In particular, the user can be sure that anything typed into the location field is never sent to Google's autocompletion servers.

I could be wrong about the things I said in this comment, though.