See https://bugzilla.mozilla.org/show_bug.cgi?id=426487 Probably we shouldn't complain about this if the connection is to localhost.

On|off line is all or nothing now... Bug 87717. I'd like to see zones, because I think there is a legitmate need to be "offline" from TCP/IP, and offline from the network (physical interfaces).

Note that in an ideal world, this would also apply to sites mapped through the magic of proxy autoconfig onto localhost/127.0.0., which would allow the running of Mochitests when offline even without a special mode or preference to ignore online/offline state; see also bug 463046.

Shouldn't that bug be also a duplicate of bug 87717 ?