Considering a subdomain "trivial" is ridiculous... there's a difference between "www.example.com" and "example.com". Not only can they serve different sites, they can even have different DNS records!
It seems that "m." is also considered a trivial subdomain. So when a user clicks a link to a "m.facebook.com" uri, they'll be confused why FB looks different when the browser reports it's on "facebook.com".
It seems that "m." is also considered a trivial subdomain. So when a user clicks a link to a "m.facebook.com" uri, they'll be confused why FB looks different when the browser reports it's on "facebook.com".
I sincerely hope Firefox doesn't follow suit.