Scroll shadows at top/bottom

After watching @leaverou talking about this technique using pure CSS, I tried to use this on a project I'm working, but the problem is, actually, that "background-attachment: local" isn't working for all browsers by now.

Issue: http://lea.verou.me/2012/04/background-attachment-local/

I decided to implement this, If you like, let me know.

Sorry for my bad english too.