I answered a this question shortly after another user had posted an answer. Both answers were similar, but my answer more explained why you had to do it rather than just how to do it.
When the other answer got accepted, I was somewhat surprised considering I had a higher score. The other answer was certainly deserving of being accepted since it was correct; when I asked the original poster of the question why he chose that answer, he said it boiled down to "the other answer was posted first".
Is this a correct way of choosing an answer to accept? Understandably, there are some cases where you will have to accept an answer based on whether it was posted first or not.