function right(e) {
  if (navigator.appName == 'Netscape' && (e.which == 3 || e.which == 2)) {
    return false;
  } else if (navigator.appName == 'Microsoft Internet Explorer' && (event.button == 2 || event.button == 3)) {
    alert("Sie haben aus Versehen die rechte Maustaste gedrückt!");
    return false;
  }
  return true;
}

document.onmousedown=right;
window.onmousedown=right;
if (document.layers) {
  window.captureEvents(Event.MOUSEDOWN);
}