The URL https://www.freebsd.org/docproj/docproj.html which used to resolve to the documentation project website now redirects to https://www.freebsd.org/docproj/docproj/ which in turn yields a 404. The correct redirect would be https://www.freebsd.org/docproj/. Looking at archive.org this redirect has been in place since early 2021. This was originally reported to the PostgreSQL project as the documentation contained this link, fixed in https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=346990ae2e9f50030831a27aba78653fbde8c7ca.
Fixed, thanks to dbaio@!
Great, thanks!