jQuery css background-position animation

Question

I've got a strange problem with jQuery and CSS; it seems a jQuery bug; I've tried to search around but infos are ugly.
There's a large photo as background of the body; when I click on a button I wish to obtain a simple jQuery animation of the background, from "bottom" position to "50%" position.
Well, if I set $("body").css("background-position", "center 50%"); it works but if I try tu use animate() jQuery function it doesn't works anymore.
So is it possible to have this effect in some way?
Thank you so much in advance.

Answer 1

I'm pretty sure it's not possible to use animate() for relative values, because it's not easily possible to calculate absolute positions from the relative information.

Try using pixel values all the way.