title: Nginx proxy configuration for offline app (appcache)
body: <p>I have an (online/offline) html app that works fine via Chrome (appcache). localhost:9999/ is served via Express.
  After first load, it works well if the express server is offline.</p>
  
  <p>Now I want the main html/css/js/png/... files gzipped via nginx proxy
  localhost/ is served via nginx(as proxy) via a redirection to localhost:9999/.</p>
  
  <p>It works well when the express server is online (gzipped).
  It fails (Bad Gateway) when the server is offline.</p>
  
  <p>Still looking for the right configuration ...
  I'm not sure if nginx handles this well.</p>
  
  <p>Thanks, Regards,
  Gilles</p>