document.observe("dom:loaded", function() {

  var form = $("form"), formElements = form.getElements(), nextField = null;

  form.observe("submit", Event.stop);

  formElements.invoke("observe", "focus", function(event) {
    var index = formElements.indexOf(this) + 1;
    nextField = formElements[index % formElements.length];
  });

  document.observe("keydown", function(event) {
    if (e.keyCode != Event.KEY_RETURN)
      return;
    if (event.element()["type"] == "submit")
      return this.up("form").submit();

    event.stop();
    nextField && $(nextField).focus();
  });

  form.select("[type=submit]").invoke("observe", "click", function() { form.submit() });

});