Seeking very simple Parallax Scrolling help...

Returning to web design after a 4-5 year absence, looks like I missed the Parallax Scrolling fad. I now need to incorporate the little bugger into what I'm building.

While I don't know Javascript per se, I've been writing HTML/CSS and adapting existing JS scripts to my needs since '98. So I Googled the subject of Parallax Scrolling and as you might imagine, there's a lot of noise out there by now. And way more functionality (and bloat) than I need for this project. Maybe someone can point me to the correct piece of code and/or tutorial to help?

I have a (fixed-size) round DIV with a bgr image that should be scrolling SLIGHTLY SLOWER than the rest of the page (when user is scrolling up or down) so as to create the illusion of depth. But I don't want the container itself to scroll more slowly. In other words, I want it to look like there was a hole punched in the site, so what's 'revealed' by the hole feels like it's an inch behind the screen. (Am I explaining this clearly enough?) And since we're scrolling vertically, the image would (of course) have to be SLIGHTLY TALLER than its containing DIV.

That's all! It doesn't need to do anything else. No automated scrolling, no delay on when the scrolling begins... I just want to be able to have a BG image scroll (vertically) at a slightly slower speed than the rest of the page. I don't even care if it can handle an image smaller than the container, since I'll make sure it overfills.

P.S.: While I'm here, could someone inform me if it's now safe to use only "border-radius" to create circles, or do we still need -moz & -webkit in the css as failsafes?