dhtml menus

Hi -

I am a little puzzled how this site implements these smooth transitions
on their menus.

http://www.activema.com/development.php

As you can see, when you mouseout of the menu, it pauses for .5 sec or
so and then scrolls up, not just disappearing. I think it is pretty
cool.

We are trying to implement this look on our site:

http://www.nfpa.com

I have figured out the opacity trick that these guys have done, but can
not seem to figure out the "scrolling" feature.

Do they use several divs that appear and disappear in sucession? Do
they make their table cells disappear in sucession?

Sorry if this is a basic question. I have googled for hours now trying
to see if anyone has written anything about this and I have yet to find
it.

Thanks,

Jamie