Since https://bugzilla.mozilla.org/show_bug.cgi?id=479880

there is no clean way for a proxy or captive portal to get a browser to display an authentication dialog when user credentials expire while he is browsing on an https website.

(to be sure, the previous methods were insecure and hackish but they existed because nothing better was available)

The IETF finally set up to fix this problem and defined a standard HTTP error that let access control equipments tell the browser authentication or re-authentication is needed and where the authentication form is located.

http://tools.ietf.org/id/draft-nottingham-http-new-status-04.txt

(since error 511 uses out-of-band authentication it is possible for the browser to only trust specific certs on error 511 and protect the user)

Please add error 511 handling in Epiphany, or have the ietf draft corrected if it's missing something

As noted by Julian Reschke in
https://bugzilla.mozilla.org/show_bug.cgi?id=562917#c21

-> <http://www.rfc-editor.org/queue2.html#draft-nottingham-http-new-status> (so the spec is approved and in the queue for publication as RFC)