> This encourages all site owners to add Vary:User-Agent to all css and js > files, whether they actually vary in content or not. > > Does anyone know the history of this recommendation? Surely that is an > inappropriate recommendation for mod_deflate. Vary:Accept-Encoding make > sense in the context of that filter, but not Vary:User-Agent.
It's because of the other (dated) canned exceptions that set/unset no-gzip/gzip-only-text/html based on the User-Agent, to second-guess browsers that send AE:gzip but can't properly deal with it.
