It’s one of those rare occasion when the three major search engines come together in an effort to improve search by agreeing on common standards.
This time, it’s the turn of duplicate content and the issue of canonicalisation. Canonical, in this context, refers to the issue of duplicate content and there’s many reasons why this may occur. For legitimate reasons, Google, Yahoo and Microsoft have now agreed a new standard tag to be used in the header section of a web page to specify the preferred URL.
All very good as it will flag up to the search engines and work in a similar way to 301 redirects, i.e. consolidate your link popularity to the preferred location.