var isNS = (navigator.appName == "Netscape") ? 1 : 0;

if(navigator.appName == "Netscape") document.captureEvents(Event.MOUSEDOWN||Event.MOUSEUP);

function mischandler(){
  return false;
}

function mousehandler(e){
	var myevent = (isNS) ? e : event;
	var eventbutton = (isNS) ? myevent.which : myevent.button;
   if((eventbutton==2)||(eventbutton==3)) return false;
}
document.oncontextmenu = mischandler;
document.onmousedown = mousehandler;
document.onmouseup = mousehandler;