function smartRollover(){
	if(document.getElementsByTagName){
	    var preload = [];
		var images = document.getElementsByTagName("img");
		for(var i=0, src, l; i < images.length; i++){
			src = images[i].getAttribute("src");
			if(src && src.match("_off.")){
				images[i].src_rollout =  src;
				images[i].src_rollover =  src.replace("_off.", "_on.");

		        l = preload.length;
		        preload[l] = new Image();
		        preload[l].src = images[i].src_rollover;

				addEvent(images[i], "mouseout", function(){this.src = this.src_rollout;});
				addEvent(images[i], "mouseover", function(){this.src = this.src_rollover;});
			}
		}
	}
}

addEvent(window, 'load', smartRollover);