Comment 134 for bug 25830

Another example of a very common server type-mislabeling trick that
inconveniences the user happens with Mailman-maintained mailing list archives.
These archives always have a monthly (or some other period) archive file that is
gzip'd text. It usually comes labeled as:

  Content-Type: application/x-gzip

instead of the correct:

  Content-Type: text/plain
  Content-Encoding: gzip

and as simple as the problem is, there is no way I've ever found to get Mozilla
to show the text instead of insisting on saving to file.

This example is Mailman bug 905910:
https://sourceforge.net/tracker/?func=detail&atid=100103&aid=905910&group_id=103

... but even if it gets fixed in Mailman, lots of Mailman sites out there will
surely be sending mislabeled files for a long time after, so the browser needs
some way for the user to cope.