sharp s and ss
I used to study German in highschool, and our teacher there thought us that writing "ss" is same as "ß". Is it correct, 'cause Duolingo doesn't recognize it?
@kcin and @gajaloc are right, there is a rule about the use of "ss" and "ß", they are different and are not freely exchangeable. It's not true, like @christian and @JacobWilliams said, that people is losing the use of ß. I live in Germany and everybody here, in official papers as in everyday writings, use it correctly. German keybords of course have the special ß character.
@scampaforche: I think you misunderstood what I said. I didn't say that the ß was disappearing. I was referring to the upper case ẞ, which is a relatively recent invention and hasn't really caught on. http://en.wikipedia.org/wiki/Capital_%E1%BA%9E Trust me, you definitely can't type this letter on a Germany keyboard. When writing in all caps, most people either use the normal lower case ß or they use SS.