Possible Duplicate:
Adding incentive for editing
Is explicitly accepting the edit of my question by some other user by "voting up the revision" a good idea?
Such edits can contribute to the question a lot but the work goes uncounted.
I have "rollback" button if I disagree the edit (never occured yet), but don't have the opposite thing.
I think a good place for voting controls is near "edited 9 hours ago" label for myself (as I see what's changed without hints) and in stackoverflow.com/posts/.../revisions page for everyone else.