All of the exim web site content is available through rsync, and this is the recommended means for mirroring the web site content.
The rsync URL is rsync://ftp.exim.org/www
However the more normal means to quote the rsync path is ftp.exim.org::www
The rsync path for the ftp area is ftp.exim.org::ftp
Your httpd obviously needs to see the mirrored content. There are also some other tweaks - Apache aliases - which are needed. The paths that need aliasing are currently only the /ftp> path which either needs pointing to your ftp mirror, or redirecting to a reasonable mirror of the exim ftp site.
If and when the mailing list archives are put on line, these may also need handling in a special way.
In some small recognition of the ISPs and other organisations who donate the web site space, bandwidth and management, the web site has a brandable component - specifically the bottom left hand pane of the main window points to the branding/branding.html file. By aliasing this path you can tailor this to put a sponsors logo in place.
Register a bug in the Exim Bugzilla under Infrastructure/Mirrors so that the mirmon information can be updated. Join the exim-mirrors list so we can tell you of any changes to mirroring practice.