function ro(el,which){
  el.src=el.getAttribute(which || "origy");
}

function ros(){
  var x = document.getElementsByTagName("img");
  for (var i=0;i<x.length;i++){
    var overy = x[i].getAttribute("overy");
    if (!overy) continue;
      
 x[i].overy_img = new Image();
    x[i].overy_img.src=overy;
   x[i].onmouseover = new Function("ro(this,'overy');");
    x[i].onmouseout = new Function("ro(this);");
    x[i].setAttribute("origy",x[i].src);
  }
}

var Preload =(window.onload)? window.onload : function(){};
window.onload = function(){Preload(); ros();}