/* Swap one image for another i.e. Rollover or Mouseover
This function uses the image's name, set in the
HTML <img> tag to access the image's place in the DOM */
function swapImages(ImageName, NewImage)
{
   /* test to see if the browser understands rollovers
   If it does swap one image for the other */

   if (document.images)
   {
   document[ImageName].src = NewImage;
   }
}