I recently installed BM 3.9 on a server, all the rest of the proxies in my
school district are 3.8 and have custom error pages, especially for 403 as
we want people to know that the site is blocked, and it isn't just their
internet connection.

Haven't found anything about custom error pages for 3.9 out there yet, and
the solutions for 3.8 won't work.

Anybody done this one yet?