Conflicting canonicals
IssueHigh priority
Pages declaring more than one canonical, pointing at different addresses.
Why it matters
The page contradicts itself about which address is the real one, so a search engine has no reason to believe either.
How to fix it
Decide which address is canonical and remove the rest. This is worse than declaring several that agree, which is merely untidy.
Skitter runs this check on every crawl, and lists each page it finds with the evidence: the header, the tag or the link that gave it away.