function menuOn(menu) {
  if (document.layers) {
    document.layers[menu].visibility = "visible";
  } else if (document.all) {
    document.all(menu).style.visibility = "visible";
  } else {
    document.getElementById(menu).style.visibility = "visible";
  }
}
function menuOff(menu) {
  if (document.layers) {
    document.layers[menu].visibility = "hidden";
  } else if (document.all) {
    document.all(menu).style.visibility = "hidden";
  } else {
    document.getElementById(menu).style.visibility = "hidden";
  }
}
function hideAll() {
  menuOff('Sub1');
  menuOff('Sub2');
  menuOff('Sub3');
  menuOff('Sub4');
}