function mouseBut(e) {
  if (event.button == 2)
  {
    if (event.srcElement.tagName=="IMG")
	{
      alert("Copyrighted Image.");
      return false;
	}
  }
}

if (document.layers) window.captureEvents(Event.MOUSEDOWN);
if (document.layers) window.captureEvents(Event.MOUSEUP);
document.onmousedown=mouseBut;
document.onmouseup=mouseBut;
window.onmousedown=mouseBut;
window.onmouseup=mouseBut;