It is common knowledge that a question only becomes "answered" when it has an answer with a score of at least +1.
Why, then, do all of the questions in the unanswered queue have no answers (or at least, on the first few pages have no answers)?
A specific example: I have a technically unanswered question, but it has an answer (currently on -1). This question no longer appears (EDIT: where it should appear) in any of the lists of unanswered questions which I can find.
EDIT: I have added the (bug) tag as I think this is a bug - the software counts a question with an answer with non-positive score as unanswered, but in a second tier. If you sort the unanswered questions by votes then questions without an answer come before those with an answer, even if that answer is very negative. Which is annoying!