var active_sub = "";

function show_sub(id, active)
{
   if(active == true)
   {
      var submenu = document.getElementById(id);
      active_sub = id;
   }
   if(active == false)
   {
      var submenu = document.getElementById(id+"_sub");
      active_sub = id+"_sub";
   }
   submenu.style.display = "block";
}

function hide_sub()
{
   var submenu = document.getElementById(active_sub);
   active_sub = "";
   submenu.style.display = "none";
}