Yes, that is correct.

Since the code is placed properly yet is still not showing up on your site make sure you:

1) Check to ensure the tpl_main_page.php is in the proper location for the template you are using.

2) The Smart Backgrounds does not override the footer file in any way with it's own code (which might override this.)

I would suspect it is probably more than likely #1 on this list.

If we can't get it figure out I can get in and take a look for you.

Just let me know.