I am an experienced web developer but I cannot seem to pull together one ability: sliding in an overlay and covering up the page content and resetting the scroll area.

Resetting the scroll area (overflow) is the piece I cannot pull off. I have looked a bit at what Facebook is doing with their light box overlays, but I have not figured all the pieces out. The keys are not scrolling to the top and allowing the overlay to scroll properly, top to bottom, no more, no less.

Any help would be greatly appreciated! I know there are tutorials out there but I have not been able to search effectively and find them. Thanks!