function tableBG(table)
{
	var rows = table.getElementsByTagName('tr');
	for(var i = 0; i < rows.length - 1; i++)
	{
		if(i%2!=0){
		var cols = rows.item(i).getElementsByTagName('td');
			for(var j = 0; j < cols.length; j++)
			{
				cols.item(j).style.backgroundColor = "#F4F4F4"
			}
		}
	}
}

window.addEvent('domready', function(){
	$$('table.arenda').each(function(table){
		tableBG(table);
	});
});