if (document.images) {
	n1on = new Image();    n1on.src = "images/nav_home_on.gif";
	n2on = new Image();    n2on.src = "images/nav_about_on.gif";
}

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