window.addEvent('domready', function() { 
		$$('#menu_nav a').each(function(el) {
		//fx
		var fx = new Fx.Tween(el,{
			duration: 500,
			link: 'cancel'
		});	
		//css & events
		el.setStyle('background-position','-20px 35px').addEvents({
			'mouseenter': function(e) {
			e.stop();
			fx.start('background-position','-20px 94px');
			},
			'mouseleave': function(e) {
			e.stop();
			fx.start('background-position','-20px 35px');
			}
		});
	});
});