I noticed on Why are vi and Emacs popular? that there is an link that points to beta. Though as that domain isn't available any more, I would suggests a database edit to change all links that is pointing to beta.stackoverflow.com, to point to stackoverflow.com instead.
I removed the beta. from DNS the other day; I figured it's been almost two years (tempus fugit!) since the start of our public beta so we should have moved on from any old links by then.
edit: I replaced all instances of beta.stackoverflow.com with stackoverflow.com so this shouldn't be a problem any more -- 2,506 posts had that content (some may have been deleted posts though).
Why not permanently redirect from beta.stackoverflow.com/* to stackoverflow.com/*?
This is another post pointing to beta