var lastmenu = "";

function closelastmenu(){
   n = document.getElementById(lastmenu);
   if(n!=null){
     n.style.visibility='hidden';
   }
}

function openmenu(id){
   m = document.getElementById(id);
   if(m!=null){
     m.style.visibility='visible';
   }
   n = document.getElementById(lastmenu);
   if(n!=null){
     if(lastmenu != id){
       n.style.visibility='hidden';
     }
   }
   lastmenu = id;
}