window.addEvent(
	"domready",
	function () {
		$$("img.button").each(
			function(navigation) {
				navigation.addEvent(
					"mouseover",
					function () {
						this.src = this.src.replace(/(\.gif|\.jpg|\.png)/, "_f2" + "$1");
					}
				);

				navigation.addEvent(
					"mouseout",
					function () {
						this.src = this.src.replace("_f2", "");
					}
				);
			}							
		);
	}
);