if (document.images)
    {
      preload_image_object = new Image();
      // set image url
      image_url = new Array();
      image_url[0] = "/nw1b.png";
      image_url[1] = "/nw2b.png";
      image_url[2] = "/nw3b.png";
      image_url[3] = "/nw4b.png";
      image_url[4] = "/nw5b.png";
      image_url[5] = "/nw6b.png";	  
       var i = 0;
       for(i=0; i<=5; i++) 
         preload_image_object.src = image_url[i];
    }