Great news for all of us struggeling to make sure that dublicate content filters are not activated (since we all know that this is really important for SEO).
Google, Yahoo and Live (Microsoft) is now supporting the new a new canonical tag, which states which URL is “the right one” for every single page onm a site.
E.g. if one of my pages can be accessed via http://www.webhaj.com/blog/?p=3 as well as via http://www.webhaj.com/blog/canonical-tag-state-your-canonical-url/- one of them will trigger the dublicate content filter. Chances are that the page filteret is not the one I would be prefer to get filteret. And if users access both pages and links both pages my SEO is hurt too, since the 2 URLs split all the link juice that should have been collected by the 1 page..
All I need to do now to make the search engines use the URL that I prefer is to add a tag like this on the page:
<link rel="canonical" href="http://yoast.com/twitter/analytics/"/>
Our friend Joost de Valk have already made some plugins to handle this easily – including for Drupal and WordPress: http://yoast.com/canonical-url-links/