Accidental offline mode
I was using Duolingo on my netbook (no extra-fancy devices for me!). At some point during a lesson, I lost my internet connection without being notified. Rather than booting me when I tried to hit "check", the lesson continued on to completion (a good 5 or 6 questions!), although audio did not play. It told me all my answers were correct, and when I "completed" the final question, Duolingo finally gave me a loading failure page and that's when I found out I had no net. I should note that I use No-Script for Firefox, and I noticed there are more scripts on Duolingo than before. While I've white-listed Duolingo itself, I don't know which others I should enable (are you guys using mixpanel for something, for example?).
Does this keep happening to you repeatedly? If yes, check your WHOLE computer. Not just one itty bitty part. The WHOLE computer. If no, don't worry about it.
What on Earth do you mean? In any case, I wouldn't have posted if I hadn't already checked to be sure it wasn't any obvious issues with my computer. It hasn't recurred, but that would require a loss of internet and I'm not going to force it to happen - replicating bugs is for the techs, not me!