function alternate(container,el,colourclass)  {
	var bgColourStyle = colourclass;
	var container = document.getElementById(container);
	var els = container.getElementsByTagName(el);
	for (var i = 0; i < els.length; i++) {
		if(i % 2 == 0) {
			if (els[i].className == '') {
				els[i].className = bgColourStyle;
			} else {
				els[i].className += ' '+ bgColourStyle;
			}
		}
	}
}
window.onload = function () {
alternate('div_container','div','alt');
alternate('table_container','tr','alt2');
alternate('para_container','p','alt3');
alternate('list_container','li','alt4');
}