| you mean horizontal as in pointing away from you? ideally your fretting hand should be relaxed enough so that the first finger can lay across the strings while you are fretting with your other fingers. If, when you are fretting, your first fingers sticks out, then you are not relaxing your hand enough. Play really, really slowly until you can get down with this.
A corrolary to this is that if you tighten your sphincter while you are playing something, you haven't quite gotten it down either. lol. | 
