MobileSafari in iOS 5 supports momentum scrolling for scrollable individual parts of the page, here is a blog post about it:

http://johanbrook.com/browsers/native-momentum-scrolling-ios...

fixed positioning is also supported in iOS5.

I am not sure why one would make an iOS5 only script-based scrolling simulation.

And you can't have a fixed-position footer while you scroll around - loads of problems there, not the least of which is that you don't get JS events until the scroll is finished. The only way around it that I'm aware of is to fake all the movement in a fixed-space page, as done here.