$(document).ready( function(){
	$.preloadImages("images/midbutton_academic_roll.jpg", "images/midbutton_distance_roll.jpg", "images/midbutton_higherlevel_roll.jpg");
	$("#midbuttons div").hover(
		function(){
			$(this).css("background-image", "url(images/"+$(this).attr("id")+"_roll.jpg)");
		},
		function(){
			$(this).css("background-image", "url(images/"+$(this).attr("id")+".jpg)");
		}
	);
});