Can't find succesful page to edit

Hey,
Maybe a stupid question, but I just bought my site. I have to edit the "succesful" page after a user have registret, either a paid registration or free. The site that gets shown at the same URL, but right after a user has signed up. I can't manage to find it. I thought that it would be in the pro-sites tab, but no. Please help.

- Nicolaj