function click (e) {
  if (!e)
    e = window.event;
  if ((e.type && e.type == "contextmenu") || (e.button && e.button == 2) || (e.which && e.which == 3)) {
    if (window.opera)
      window.alert("Tut uns leid: Diese Funktion ist deaktiviert.");
    return false;
  }
}
if (document.layers)

document.captureEvents(Event.MOUSEDOWN);

i=0;

for(var i in document.images) {
document.images[i].onmousedown = click;
document.images[i].oncontextmenu = click;
i++;
}