This is most likely due to you using an older version of UberCMS, and Habbo deleting all their style related files as UberCMS linked them directly from Habbo. You'll either have to find a more current version, or go rip the page styles off other hotels and host them locally.
Yes, You're using another hotels database, I've seen many have this error, Simply go to your users table and click the red empty button, and re-sign up.
There will also be rooms and stuff that people have left.