Event.observe(window, 'load', function(){
	$$('#main_menu li').each(function(e){	
		if (e.down('menu',0)) {
			e.observe('mouseover', function(){
				e.down('menu',0).setStyle({display: 'block'});
			})
			e.observe('mouseout', function(){
				e.down('menu',0).setStyle({display: 'none'});
			})
		}
    })
});