So I bet you all met into a scenario, where someone wrote a good, detailed answer which answers part (or most, or the core) of your question. Then should you mark it as accepted? Or should you just don't accept it immediately, and wait if he updates the question or other better answers are written. As a question which's marked with an accepted answer might make people don't click into it.
What you accept as an answer is up to you. It is your accept vote and it only indicates that the specific answer helped you most. By that definition the answer doesn't strictly need to answer all of what you asked in your question. No one else can or should decide for you if an answer helped you.
But it does help future visitors if your question has complete answers that address all aspects of your question without your question itself being too broad.
Before you accept an partial answer consider and verify the following concerns:
- Did the user who provided an answer overlooked something important? A comment can help to get that confirmation
- Is your question maybe to blame for the kind of answers you got? Inform the participants and foremost edit your question (either improve or remove unclear parts) so future visitors will not have the same confusion
- Is your question focused enough on a single topic? If questions lack focus / are a bit broad, answerers might stick to the bits they can manage to write an answer for in under an hour or so.
- Is the part that wasn't addressed maybe a good fit for a follow up question? In that case ask a new question and make sure to link back to your now answered question.
- Did you wait long enough? Some high traffic sites have highly effective users that start out their answer with a few reasonable text-blurbs (some call this the Fastest Gun In The West) and then expand/revisit their answer in the next hours/days.
If none of the above apply and you're happy enough that you got a substantial part answered, accept the answer. There is no obligation to accept an answer. If you feel the question is valid as it stands and none of the answers address the topic at hand to your liking, do not cast an accept vote. Consider casting an up vote if you found an (partial) answer useful.