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;