Inserts canonical link code into header. After activation, from your WordPress Settings, change Permalinks to Custom Structure: **/%postname%/
To verify that the canonical link has been activated properly you will need to use Firefox which I highly recommend anyways ( http://www.mozilla.com/?from=sfx&uid=266924&t=318 ) to check for a "C" to the right of URLs in the URL bar in your browser with this SEO add-on: https://addons.mozilla.org/en-US/firefox/addon/321/.
Learn more about the canonical link from Google: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=139394
How to have SEO-Friendly URLs in WordPress:
For more help or suggestions, please visit the Support Forum: