function table_bg(table_id) {
	var tab = document.getElementById(table_id);
	if (!tab) return;
	var rows = tab.getElementsByTagName('tr');
	for (var i = 0; i < rows.length; i++) {
		if(i%2==0) {
			rows.item(i).style.backgroundColor = "#ededed";
		}
		else {
			rows.item(i).style.backgroundColor = "#ffffff";
		}
	}
}