Crosspost from http://meta.stackexchange.com/q/6610 as suggested
Note that SO/SU/SF/MSO are all broken, but Metas SU/SF and Web Apps are fine. Not sure if that's tied to my login, so here's a screenshot:
The problem appears to be that while the working icons are
- http:// sstatic.net/superusermeta/img/favicon.ico
...the non-working ones are missing the img subdir in the path:
- http:// sstatic.net/superuser/favicon.ico
and I note that http://sstatic.net/superuser/img/favicon.ico does work.