function swapTopImage() {
  var topImg = arguments[0];
  // since we're interposing this method before the MM_swapImage, save off
  // the arguments, and we'll hand them into MM_swapImage when we're done.
  var arg1 = arguments[1];
  var arg2 = arguments[2];
  var arg3 = arguments[3];
  var arg4 = arguments[4];
  document.TopOver.src = topImg;
  MM_swapImage(arg1, arg2, arg3, arg4);
}

function topImageRestore() {
  document.TopOver.src = 'images/site/top_blank.gif';
  MM_swapImgRestore();
}