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goog's webmaster tools is listing two versions of each of my sites
If both versions directly show content with "200 OK" status, you have a problem that needs to be fixed.
If one of them has a page-by-page redirect to the other, then all is OK.
[edited by: phranque at 8:22 pm (utc) on Aug 12, 2013]
[edit reason] exemplified domain [/edit]
I have this same issue.
And I have a functioning 301 redirect in place from non-www. to www.