Mixed order and locking question

I have been wondering this for a while. I have noticed that usually when you post a question and people respond, the list is usually chronological as the person who responds first to the question is on the top and then it goes down the page, but I have noticed that some responses to the question are on the top of the page even though they were made much later than responses below it? Why is this? Another thing I wonder is do questions get locked by the site supervisors when the question starts to become irrelavent or too long? Please give suggestions. Thank You.

an answer that is rated helpful is automatically moved to the top of the page. and if another answer is rated helpful as well, the current helpful one at the top goes back to it's normal place and the new helpful answer is moved to the top. and usually they're locked if they get too long because most of the time it gets off topic, or arguments are getting started. they just want to keep the peace going.. no need for fights :]

Questions with higher ratings get bumped up.

Like Tina said, higher rated questions are bumped up and advisors lock questions when people start to get rude or argumentative...