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;