function addClass(element,name) {
  if (!element.className) {
    element.className = name;
  } else {
    element.className+= " ";
    element.className+= name;
  }
}
function stripeTables() {
  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) {
      addClass(rows[j],"odd");
    }
  }
}
window.onload=stripeTables;