function imgRollover() {
if(document.getElementsByTagName) {
var images = document.getElementsByTagName("img");
var imglength = images.length;
var image_cache = {};
for(var i=0; i < imglength; i++) {
if(images[i].className=="btn"){
var imgsrc = images[i].getAttribute("src");
if(!image_cache[imgsrc]){
image_cache[imgsrc]= new Image();
image_cache[imgsrc].src = imgsrc.replace("_out.", "_over.");
images[i].onmouseover = function() {this.setAttribute("src", this.getAttribute("src").replace("_out.", "_over."));}
images[i].onmouseout = function() {this.setAttribute("src", this.getAttribute("src").replace("_over.", "_out."));}
}
}
}
}

if(document.getElementById){
  images = document.getElementById('imageField');
  imgsrc = images.getAttribute("src");
  image_cache[imgsrc]= new Image();
  image_cache[imgsrc].src = imgsrc.replace("_out.", "_over.");
  images.onmouseover = function() {this.setAttribute("src", this.getAttribute("src").replace("_out.", "_over."));}
  images.onmouseout = function() {this.setAttribute("src", this.getAttribute("src").replace("_over.", "_out."));}
}

}
if(window.addEventListener) {
window.addEventListener("load", imgRollover, false);
}else if(window.attachEvent) {
window.attachEvent("onload", imgRollover);
}