Why do we block browsing of the documentation directories? - Mailing list pgsql-www

http://www.postgresql.org/files/documentation/pdf/8.3/
gives me
Forbidden
You don't have permission to access/files/documentation/pdf/8.3/ on this server.

Why, do we have something to hide?  It would be very nice to be able to
see what versions of the docs are available.
        regards, tom lane