I Know I will get a -1 reputation for downvote, but sometimes I will not get any -1 rep. On what criteria downvote operate ? Today I flagged the answer and downvote it and I got a -1 reputation, but before this week I had a same thing but without -1 rep, Please clarify it!!
Only down-voting an answer reduces your reputation, and only when the answer is not a CW (Community Wiki). Down-voting a question, or a CW answer doesn't give you any -1.
Keep in mind that a vote is blocked after X minutes you cast it. If you try to down-vote a post that you already up-voted earlier, the down-vote is not recorded, and you don't get any -1.
