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;