The Canonical URL Meta Tag revealed on Friday, February 20th 2009 is a new Meta Tag announced by Google, MSN, and Yahoo that will deal with some complicated duplicate content issues. This new tag, added to the <head> section of your HTML document will tell search engines exactly what URL you would like this page to be indexed as. Meaning if you have a long URL, or a URL containing parameters you can have it indexed as the URL you specify in the Canonical Meta Tag, rather than having it indexed more than once as different URL's.
