If I were interviewing you and you said "I don't know" I would say "try to work it out". Jumping ahead and saying "I don't know but I think I can probably..."

If I were interviewing you and you said "I don't know" I would say "try to work it out". Jumping ahead and saying "I don't know but I think I can probably..." will earn you a few extra points. I recall one interview where I asked what sort of responses an HTTP GET might result in. The candidate knew 200 and 404 but that was about it. Then I asked, "If you were writing the HTTP standard, what other responses might you include" and he told me about HTTP 304 Not Modified and the related cache-* headers, which he was clearly re-inventing on the spot. I scored him very highly for that.