Scrolling up and behind 'sticky' objects-- but not to top of page. Advice, scripts?

[siran]

Have also been experimenting a little bit.
My solution can not fade, it just clips. And it looks jerky in preview and IE 9 (and I guess also on mobile devices).
Maybe someone still might find it useful?
I don't even try to create a good looking example.
There is some code at the page head and the green rectangle has the name htmlclass=clipTop applied.
In the code there is a hard coded 20, this defines the offset from the top where the objects with that name are clipped.