function newImage(arg) {
   if (document.images) {
      rslt = new Image();
      rslt.src = arg;
      return rslt;
   }
}

function changeImages() {
   if (document.images && (preloadFlag == true)) {
      for (var i=0; i<changeImages.arguments.length; i+=2) {
         document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
      }
   }
}

var preloadFlag = false;
function preloadImages() {
   if (document.images) {
      prev_image_over = newImage("/images/prev-image-over.gif");
      index_over = newImage("/images/index-over.gif");
      next_image_over = newImage("/images/next-image-over.gif");
      preloadFlag = true;
   }
}