no statistics/function in Firefox 21.0

This was due to being logged in to WordPress. I found information about that here https://evansolomon.me/notes/faster-wordpress-multisite-nginx-batcache/. Batcache uses cookies for this purpose, so it’s not enough to log out. The cookie needs to be cleared too. I found info about that here https://whitewp.com/tag/batcache/. Both those pages contain other information about WP caching that I found useful.