if (document.images) 
{
   img1 = new Image();
   img2 = new Image();
   img3 = new Image();
   img4 = new Image();
   img5 = new Image();
   img6 = new Image();
   img7 = new Image();
   img8 = new Image();
   img1.src = "images/01nav-on.gif";
   img2.src = "images/02nav-on.gif";
   img3.src = "images/03nav-on.gif";
   img4.src = "images/04nav-on.gif";
   img5.src = "images/bg-header.gif";
   img6.src = "images/btn-roll.gif";
   img7.src = "images/btn-top.gif";
   img8.src = "images/btn-home-roll.gif";
}