function clickIE4(){
  if (event.button==2) return false;
}
function clickNS4(e){
  if ((document.layers||document.getElementById&&!document.all) && (e.which==2||e.which==3)) return false;
}
if (document.layers) {
  document.captureEvents(Event.MOUSEDOWN);
  document.onmousedown=clickNS4;
}
else if (document.all&&!document.getElementById) {
  document.onmousedown=clickIE4;
}
document.oncontextmenu=new Function("return false")