function stripeTables() {
  if (!document.getElementsByTagName) return false;
  var tables = document.getElementsByTagName("table");
  for (var i=0; i<tables.length; i++) {
    var rows = tables[i].getElementsByTagName("tr");
    for (var j=0; j<rows.length; j=j+2) {
      rows[j].className = "odd";
    }
  }
}

window.onload = stripeTables;