if (document.images)
{
  preload_image_object = new Image();
  // set image url
  image_url = new Array();
  image_url[0] = "/img/plant-gallery.jpg";
  image_url[1] = "/img/plant-gallery-over.jpg";
  image_url[2] = "/img/planter-gallery.jpg";
  image_url[3] = "/img/planter-gallery-over.jpg";
  image_url[4] = "/img/create-office.jpg";
  image_url[5] = "/img/create-office-over.jpg";
  image_url[6] = "/img/grow-atmosphere.jpg";
  image_url[7] = "/img/grow-atmosphere-over.jpg";
  image_url[8] = "/img/living-walls.jpg";
  image_url[9] = "/img/living-walls-over.jpg";
  image_url[10] = "/img/photo-gallery.jpg";
  image_url[11] = "/img/photo-gallery-over.jpg";
   var i = 0;
   for(i=0; i<=3; i++) 
     preload_image_object.src = image_url[i];
}