window.addEvent('domready', function() { 
	$$("img.menu").forEach(function(element){
             element.addEvents({
               	'mouseenter': function() {element.src = element.src.replace('_f1.jpg','_f2.jpg')},
               	'mouseleave': function() {element.src = element.src.replace('_f2.jpg','_f1.jpg')}
		});
	});
});