// preloading images
if (document.images) { 
img1on=new Image();
img1on.src="/images/nav/nav-1a.gif";
img2on=new Image();
img2on.src="/images/nav/nav-2a.gif";
img3on=new Image();
img3on.src="/images/nav/nav-3a.gif";
img4on=new Image();
img4on.src="/images/nav/nav-4a.gif";

img1off=new Image();
img1off.src="/images/nav/nav-1b.gif";
img2off=new Image();
img2off.src="/images/nav/nav-2b.gif";
img3off=new Image();
img3off.src="/images/nav/nav-3b.gif";
img4off=new Image();
img4off.src="/images/nav/nav-4b.gif";
}

// function to activate images
function imgOn(imgName) {
	if (document.images) {
	document[imgName].src=eval(imgName+"on.src");
	}
}

// function to deactivate images
function imgOff(imgName) {
	if (document.images) {
	document[imgName].src=eval(imgName+"off.src");
	}
}