This is suggestion about zenphoto.org.

Accidentally i entered http://www.zenphoto.org/\, it is showing database error instead of 404 error.

Hm, that probably should not happen. That will be a Zenphoto issue. But as long as there is a db error it is at least catched.

It is not doing that now. Do you remember what the database error was?

I have sent a mail about that.