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

i0a=new Image();
i0a.src="images/butt1.gif";
i0b=new Image();
i0b.src="images/butt1a.gif";

i1a=new Image();
i1a.src="images/butt2.gif";
i1b=new Image();
i1b.src="images/butt2a.gif";

i2a=new Image();
i2a.src="images/butt3.gif";
i2b=new Image();
i2b.src="images/butt3a.gif";

i3a=new Image();
i3a.src="images/butt4.gif";
i3b=new Image();
i3b.src="images/butt4a.gif";
}

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")
}}