[malandrew]

Ooops. I hit down vote instead of up vote by accident. How do I undo it?

[maaku]

You can't. Welcome to the post-500 club.

[malandrew]

Really? You can't undo votes only after you pass 500? What's the logic in that?

[maaku]

You can't undo votes period, as far as I know (please correct me if I'm wrong).

500 karma is when you get the ability to down-vote.

[MartinCron]

I upvoted the parent for you. It all evens out.

[pavel_lishin]

Thus begins the HackerNews vote blackmarket.