function smartRollover() {
	if (document.getElementsByTagName) {
		var images = document.getElementsByTagName("img");

		for (var i=0; i < images.length; i++) {
			if (images[i].getAttribute("src").match("-off.")) {
				
				images[i].onmouseover = function() {
					this.setAttribute("src", this.getAttribute("src").replace("-off.", "-on."));
				}
				
				images[i].onmouseout = function() {
					this.setAttribute("src", this.getAttribute("src").replace("-on.", "-off."));
				}
			}
		}
	}
}

if (window.addEventListener) {
	window.addEventListener("load", smartRollover, false);
} else if (window.attachEvent) {
	window.attachEvent("onload", smartRollover);
}