Anything that's not officially approved or accepted is uncertified. Don't celebrate winning that close election just yet — the results are still uncertified, so there might be a recount.
When something is certified, it's been declared to be authentic or official, like a certified letter. When a person is certified, they've met a certain standard, like a certified accountant. Add the prefix un- ("not") and you get the opposite, something or someone who's failed to meet this standard of authenticity or expertise. If your school hires uncertified teachers, they may not be as well-educated as you'd like them to be.