window.addEvent('domready', function(){
	$$('li[id^=bt_]').each(function(el){
		var item = el.id.replace('bt_','');
		if($('sub_'+item)){
			$('sub_'+item).hide();
		
			el.addEvents({
				'mouseenter':function(){
					$('sub_'+item).show();
				},
				'mouseleave':function(){
					$('sub_'+item).hide();
				}
			})
		}
	});
});