function click(e) {
  if (document.all) {
    if (event.button == 2 || event.button == 3) {
      oncontextmenu = "return false";
    }
  }
  if (document.layers) {
    if (e.which == 3) {
      oncontextmenu = "return false";
    }
  }
}
if (document.layers) {
  document.captureEvents(Event.MOUSEDOWN);
}
document.onmousedown = click;
document.oncontextmenu = new Function("return false;");