Which kind? There are three types of that effect. The first, and best, doesn't work in IE; if you're using IE you won't have seen it. It involves using the CSS attribute position:fixed to fix the menu in one place.
i tried to use it,
its top positioning is not working finely.
i set left 0px top 100 px z index 2
and the menu appears on the top
not 100 px down
what might be wrong in that can u please see it.