I have define_page_4.php in the drop down in define pages editor. The question is, what would be the URL to this page?

I've designed a custom page and edited page_4 but when I direct to http://www.limelites.co.uk/index.php?main_page=page_4 I just get a blank page with none of my editing?

Also, would there be an easy way to call this page from my script:

setTimeout( "window.location.href = '<?php echo zen_href_link(FILENAME_PAGE_4, '', 'NONSSL'); ?>'", 3*1000 );

Basically, what's the URL to define_page_4.php ??