$(document).ready(function(){
	//rollover hande ( eg. nav1.jpg => nav1_on.jpg )
	var OverHandle = "_on";

	//preloading
	$('.rollover').each(function(){
		var ext = "";
		ext = "." + this.src.substr(this.src.length-3,3);
		$(this).preload({
			find: ext,
			replace: OverHandle+ext
		});

		$(this).hover(function(){
			var ext = "";
			ext = "." + this.src.substr(this.src.length-3,3);
			this.src = this.src.replace(ext,OverHandle+ext);
		},function(){
			this.src = this.src.replace(OverHandle,"");
		});
	});

});