I just downvoted a question I found a bit ridiculous, and when I clicked on my profile and looked at my reputation tab, it said "-1 reputation". I don't know what my reputation was beforehand, but do I lose reputation when I downvote? If so, is there a reason why?
You do not lose reputation for downvoting a question. You do lose reputation for downvoting an answer. You can find more here.
You lose reputation when:
- your question is voted down: −2
- your answer is voted down: −2
- you vote down an answer: −1
- you place a bounty on a question: − full bounty amount
- one of your posts receives 6 spam or offensive flags: −100
This Meta.SE question also has more information.