code: function alertMessage_(message, cssClass) {
    var alertBox = $('<div></div>')
        .addClass(cssClass)
        .css('display', 'none')
        .text(message);
    $('#alert-messages').prepend(alertBox);
    alertBox.fadeIn({
      complete: function() {
        setTimeout(function() {
          alertBox.slideUp();
        }, 3000);
      }
    });
  }
docs: Displays for a few seconds a box with a specific message and then fades
  it out.
  @param {string} message Small message to display.
  @param {string} cssClass The class(s) to give the alert box.
  @private