How is it possible that the function of the test page works, but it does not go live?

Try changing your script to this since you’re not actually running a cross-browser request:

<script>
(function($) {
  $(document).ready(function() {
    var refreshId = setInterval(function()
    {
      $('#content').fadeOut("fast").load('/new.php').fadeIn("fast");
      $("#content .span9 article").unwrap();
    }, 10000);
  });
})(jQuery);

UPDATE: Wrapped in WP-friendly jQuery no-conflict code…