function operateMenu() {
		var menu=document.getElementById('menu');
		var Links=menu.getElementsByTagName('A');
	
		for(var i=0; i<Links.length; i++) {
			Links[i].onclick=function() {
				var Lists=this.parentNode.parentNode.getElementsByTagName('UL');
	
				for(var j=0; j<Lists.length; j++)
					Lists[j].style.display='none';
	
				if(
					this.nextSibling && this.nextSibling.nextSibling &&
					this.nextSibling.nextSibling.tagName=='UL'
				)
					this.nextSibling.nextSibling.style.display='block';
			}
		}
	}