var ns4 = ( document.layers ) ? 1 : 0
var ie4 = ( document.all ) ? 1 : 0
var noClickMessage = 'Pop up menu disabled.';

function click( e ) {
  if( ie4 ) {
    if( event.button == 2 ) {
      alert( noClickMessage );
      return false;
    }
  }
  if( document.layers ) {
    if( e.which == 3 ) {
      alert( noClickMessage );
      return false;
    }
  }
}

if( ns4 ) document.captureEvents( Event.MOUSEDOWN );
document.onmousedown = click;