var timeout	= 500;
        var closetimer	= 1000000;
        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; 
        
 
	function changeVisibility()
	{
		document.getElementById("m1").style.visibility="hidden";
	}