var timeout	= 500;
	var closetimer	= 500;
	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;