Thanks, this is useful. It's weird you are getting a 403 on the typekit request. It looks like the font-loader probably just times out. Do you happen to have any extensions that might strip referrer
Bingo. That's the problem. Sorry, I figured starting Firefox in safe mode reverted my custom config. I had disabled referrer via about:config's network.http.sendrefererheader. Changing that value back to '2' (send referrer headers always) eliminates the problem. I guess only amongst HN readers can you count on people not sending this header. Anyhow, if TypeKit could not require this, that would be great. Thanks for looking into this, even though it might only help .001% of users.