var old=null;
function changemenu(mydiv){
  var obj = document.getElementById(mydiv);
  //if (old!=null&&old!=obj)
    //old.style.display='none';
  //old=obj;
  if (obj.style.display=='none'){
    obj.style.display='block';
  }else{
    obj.style.display='none';
  }
}