Last modified: 2014-04-20 08:23:37 UTC
From bug 49720 comment 7. To deploy faster to all users, needs a Last-Modified header. Right now browsers are told to basically cache it unconditionally so nobody will get the new content until their cache is manually purged.
Same as https://bugzilla.mozilla.org/show_bug.cgi?id=167808 ?
I don't plan to work on this -> Setting lowest priority.
The Last-Modified header is currently correctly sent. In the future it might be replaced with adding ?mtime to css/js URLs.