Positioning shapes on the backgroud of a webpage randomly using CSS

[d|b]

Hi there,

I would like to have a few 2d coloured shapes that are placed randomly on the x and y axis of the back ground of this website:

http://www.acloud.tumblr.com

Every time the page loads, the shapes are positioned and (maybe also rotated would be even better) at random co-ordinates across the screen.

This would obviously be happening in a layer below the main content, which would be unaffected by this movement

I was thinking that maybe some javascript for the randomiser and CSS for the positioning could do the trick. Any specific ideas on how I might be able to do this?

Thanks