[CONTRIBUTION] Ultimate SEO URLs v2.1 - by Chemo in General Add-Ons Support Posted May 25, 2010 Look in the includes/configure.php file for this line define('DIR_WS_HTTP_CATALOG', ''); If you find it, exactly as it is, then your configure file is setup incorrectly. See here on how to fix it. The code in includes/classes/seo.class.php has to be changed to rewrite a url that isn't already included. But this contribution includes most that are needed. What are you wanting to rewrite? Got it working, many of the pages still include .php for an extension. Looking to rewrite category pages to contain category name.