It means that file was either not uploaded to the server, or the path to that file is incorrect where it is refrenced on line 1 of users_registration.php (and probably all other pages since the pages al refer to the same location).
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.