function swapImage(event) {
	if (event.type == 'mouseover') {
		event.target.src = '/images/order_hover.gif';
	} else {
		event.target.src = '/images/order.gif';
	}
}

Event.observe(window, 'load', function() {
	var order = Try.these(
		function() { return $('order') }
	)
	if( order ) {
		Event.observe('order', 'mouseover', swapImage);
		Event.observe('order', 'mouseout', swapImage);
	}
});