if ((navigator.userAgent.indexOf("Mozilla/4.0")!=-1)||
(navigator.userAgent.indexOf("Mozilla/3.0")!=-1)) {

im1a=new Image();
im1a.src="images/nav_01a.jpg";
im1b=new Image();
im1b.src="images/nav_01b.jpg";

im2a=new Image();
im2a.src="images/nav_02a.jpg";
im2b=new Image();
im2b.src="images/nav_02b.jpg";

im3a=new Image();
im3a.src="images/nav_03a.jpg";
im3b=new Image();
im3b.src="images/nav_03b.jpg";

im4a=new Image();
im4a.src="images/nav_04a.jpg";
im4b=new Image();
im4b.src="images/nav_04b.jpg";

}
function ImgEffect(img1,img2)
{
if ((navigator.userAgent.indexOf("Mozilla/4.0")!=-1)||
(navigator.userAgent.indexOf("Mozilla/3.0")!=-1)) {
document.images [img1].src=eval(img2 + ".src")
}}