9.4.17 Loader (std_loader)
Displays a small loading overlay when jQuery Mobile loads in content via AJAX, or when you want to perform an action that momentarily blocks user interaction.
You use JavaScript to start/stop the loader weblet:
Lstd.Weblets.stdLoader.start(my_id); // Displays the loader with an id of "my_id"
Lstd.Weblets.stdLoader.stop(); // Stops theactive laoder