Maybe I'm missing something but an example would be this question about rails:
with the selected answer from 2009.
I'm sure there's now a better way to do this, is there a way to bump it?
If you're looking for an updated answer, you can:
If you have an updated answer, you can:
Just post it as an answer. If it's dramatically different from an existing answer, it's unlikely that you'll be able to edit it into something. Also, posting a new answer bumps the question to the home page as well, so any visitors who do end up viewing the question will spot your new answer and vote on it accordingly.
If it's a minor change such as a version number, you can just edit it directly into the post or add a comment to the post so that visitors can see that note.
You shouldn't downvote old, outdated answers though.
Update the old answer and add a comment
"No longer valid post release X.Y."
Then write the new answer, and include a comment such as,
"Note: This applies to releases X.Y and forward."
(Thanks to commenters who pointed out to me that a downvote is not correct!)