if (document.images) {
   img1 = new Image(); img1.src = "i/t1-1b.png";
   img2 = new Image(); img2.src = "i/t1-2b.png";
   img3 = new Image(); img3.src = "i/t2-1b.png";
   img4 = new Image(); img4.src = "i/t2-2b.png";
   img5 = new Image(); img5.src = "i/t2-3b.png";
   img6 = new Image(); img6.src = "i/t2-4b.png";
   img7 = new Image(); img7.src = "i/t3-1b.png";
   img8 = new Image(); img8.src = "i/t3-2b.png";
   img9 = new Image(); img9.src = "i/t4-1b.png";
   img10 = new Image(); img10.src = "i/t4-2b.png";
   img11 = new Image(); img11.src = "i/t4-3b.png";
   img12 = new Image(); img12.src = "i/t4-4b.png";
   img13 = new Image(); img13.src = "i/t4-5b.png";
   img14 = new Image(); img14.src = "i/t4-6b.png";
   img15 = new Image(); img15.src = "i/t5-1b.png";
   img16 = new Image(); img16.src = "i/t5-2b.png";
}
function setImage(img, image) {
   if (img) {
      img.src = image;
   }
}