var preloaded_images = $A();

function init_rollover()
{
  var toggle = function(img, original, another){
    return function(){
      if (img.src == original) {
        img.src = another;
      } else {
        img.src = original;
      }
    }
  };

  var preload = function(img, another){
    var holder = new Image();
    holder.src = another;
    preloaded_images.push(holder);
  };

  var buttons = $$('.rollover');

  buttons.each(function(button){
    var img = button.getElementsByTagName("img")[0];
    var rel = button.readAttribute("rel");
    if(img){
      var another = "";
      var original = img.src;
      if (rel && rel.match(/rollover\[(.*)\]/)) {
        another = RegExp.$1;
      } else {
        if (img.src.match(/_on\./)){
          another = img.src.sub(/_on\.(png|gif|jpg)$/, "_off.#{1}");
        } else {
          another = img.src.sub(/_off\.(png|gif|jpg)$/, "_on.#{1}");
        }
      };
      
      preload(img, another);
      button.onmouseover = toggle(img, original, another);
      button.onfocus = toggle(img, original, another);
      button.onmouseout = toggle(img, original, another);
      button.onblur = toggle(img, original, another);
    }
  });
}

Event.observe(window, "load", init_rollover, false);