if (document.images) 
{
   img1 = new Image();
   img2 = new Image();
   img3 = new Image();
   img4 = new Image();
   img5 = new Image();
   img6 = new Image();
   img7 = new Image();
   img1.src = "images/nav_r1_c2_f2.jpg";
   img2.src = "images/nav_r1_c4_f2.jpg";
   img3.src = "images/nav_r1_c5_f2.jpg";
   img4.src = "images/nav_r1_c6_f2.jpg";
   img5.src = "images/nav_r1_c8_f2.jpg";
   img6.src = "images/nav_r1_c9_f2.jpg";
   img7.src = "images/nav_r1_c11_f2.jpg";
}