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);
}

// source by primavista