Assume that, I get an answer to my question that is OK, and i accept it. After a while I get another answer that is seemed to be more OK.
Now what should I do? Should I accept the new answer? If I accept what will happen to the earned reputation of the 1st answerer?
If user A comes along and answers your question, and you accept it, he gets 15 reputation. If user B then adds an answer and you accept his answer instead, user A will lose 15 reputation and user B will gain 15 reputation.
This can cause hard feelings (it is amazing how much people care about stupid internet points!) so what I recommend is waiting awhile before accepting an answer. Often times a better answer will come along.
Don't over think this, the accept mark is yours to do with what you want (okay, so there are rare exceptions, but those are rare enough I won't go into them). If you accept user A's answer, it is perfectly fine to leave it that way, even if user B adds a better answer later. And, on the other hand, it is perfectly acceptable to unaccept user A's answer and accept user B's answer. The check mark’s only purpose is to show what helped you and solved your problem, it doesn't matter what order the answers came in.
Try to accept whatever has helped you the most. That's what it's supposed to mean but it's really down to your interpretation.
Timeliness could well be part of that utility and I know —from painful experience— that there are a lot of very good answers that haven't been accepted because they're an hour or two late to the pack.
But if we're talking minutes and you see two new answers at the same time, pick the better post, not the one that was there seconds earlier than the other.
