function MenuOn(x) {
  MenuReset();
  m = "m" + x;
  document.getElementById(m).style.visibility = 'visible';
}

function MenuOff(x) {
  m = "m" + x;
  document.getElementById(m).style.visibility = 'hidden';
}

function MenuReset() {
  //var all_m = new Array(); in head tag
  for (i = 0; i < all_m.length; i++) {
    m = "m" + all_m[i];
    document.getElementById(m).style.visibility = 'hidden';
  }
}