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