Duolingo does not open in Firefox 57
Any idea what's going on and how to fix this?
I had the same problem after updating Firefox.
Strangely it only happened on Duolingo.
Every page with the new code didn't work but pages running on the old code did. (the discussion forum still runs on the old code)
I had to reset Firefox to the default settings after that it re-worked.
Why, I can't say, it is very strange, even deactivating every add-on or extension (I had only two actually) didn't work either.
That did the trick, thanks much. Interestingly, I did a search on "firefox" in this forum prior to posting my question, and nothing recent came up.
I also use Firefox 57 on MacOS 10.12.6. Without any problems. Maybe you have some add-ons like NoScript or uMatrix active?