$(document).ready(function() {
 function preload(images) {
  $(images).each(function(){
   $('<img/>')[0].src = this;
  });
 }

 preload('callout-fruit-drinks-on.png', 'callout-juices-on.png', 'callout-teas-on.png', '/images/school-bus.gif'); // Preload main image

 $("#school-bus").css({backgroundPosition: "113px 0"}).mouseover(function(){
  $(this).stop().animate({backgroundPosition: "0 0"}, {duration: 500});
 }).mouseout(function(){
  $(this).stop().animate({backgroundPosition: "113px 0"}, {duration: 500});
 });

}); // document.ready()