What wrong I did but don't know why my reputation doesn't increase after my answer is up-voted. This shows up-votes in my answer but couldn't be changed my reputation. Note to my reputation before up-vote and vote my answer to see my reputation is still as before. How does this CSS produce a circle?
That answer has been changed to a Community Wiki post because it was edited too many times (note the revision comment), and you unfortunately won't gain any further reputation once a post becomes Community Wiki.
You could consider flagging your answer and asking a moderator to remove Community Wiki status (they may or may not actually do so, but it's worth a try if you feel all of your edits were legitimate).
See also: What are "Community Wiki" posts?