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("Spiacenti, il tasto destro del mouse e' disabilitato");
   return false;
}
return true;
}

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