var timeout	= 500;
var closetimer	= 0;
var ddmenuitem	= 0;
		
// open hidden layer
function mopen(id){	
	// cancel close timer
	mcancelclosetime();
		
	// close old layer
	if(ddmenuitem) ddmenuitem.style.visibility = 'hidden';
		
	// get new layer and show it
	ddmenuitem = document.getElementById(id);
	ddmenuitem.style.visibility = 'visible';
		
}

// close showed layer
function mclose(){
	if(ddmenuitem) ddmenuitem.style.visibility = 'hidden';
}
		
// go close timer
function mclosetime(){
	closetimer = window.setTimeout(mclose, timeout);
}
		
// cancel close timer
function mcancelclosetime(){
	if(closetimer){
				window.clearTimeout(closetimer);
				closetimer = null;
	}
}
		
// close layer when click-out
document.onclick = mclose;