function addClassToOddRows (table, className) {
	var rows = table.getElementsByTagName('tr');
	for (var i = 0, l = rows.length; i < l; i = i + 2) {
		rows[i].className += ' ' + className;
	}
}

function initZebra () {
	var zebras = [];
	var tables = document.getElementsByTagName('table');
	if (tables.length) {
		for (var i = 0, l = tables.length; i < l; i++) {
			if ((/\bzebra\b/).test(tables[i].className)) {
				addClassToOddRows(tables[i], 'odd');
			}
		}
	}
}

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