What is the guestbook ID (or URL)? I tried to check the guestbook associated with your email but it appears be working.
There are two possibilities here:
- Someone has left a message which somehow forwards the user to an adult site. In this case there is a bug in the guestbook system, since "dangerous" html, javascript etc is supposed to be removed from all posts.
- Someone accessed to the members area using your email and your password, and changed the header of your guestbook. Javascript etc is allowed here which makes redirects possible. This would not be a bug in the system.