Is there an option to receive a notification, when a post you downvoted was edited?
With a downvote you suggest that something is wrong, after the poster edited it, maybe there is no reason anymore for the downvote.
If you are willing to get a somewhat enlarged range of notifications, you can subscribe to the RSS feed for that Question (this will notify you not only of edits to the Question, but new & edited Answers; however Comment activity does not appear to trigger notification). You'll need an RSS client, such as Google Reader, to receive such a feed.
Even more complicated/general notifications were mentioned in this meta Question.