You could always leave the simple color swap you have now for default and then use CSS3 for the browsers that like it:
transition: background-position
http://www.impressivewebs.com/demo-f...mated-sprites/
If you want to use jQuery like you are trying to do, you are moving the wrong thing.
Code:
jQuery('ul#sections li#who').hover(function() {
jQuery(this).stop().animate({
marginTop : '-182px'
That moves the <li> itself. You want to animate the background-position of the <li> instead.