Google, Yahoo & Microsoft all agree on something. Huh?

Posted At : May 6, 2009 7:44 AM | Posted By : Dan Dawes
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goole yahoo msn logos Back in February, with relatively little fanfare, the big three in search all agreed on supporting a new HTML tag to help reduce duplicate content on the web. That tag is referred to as a "canonical" tag. Canonic is defined as "conforming to orthodox or recognized rules." Makes sense to me, so what's it all about.

Basically, there are lots of ways a web page's URL can play out depending on how your hosting server is setup, what programming languages your site uses, what type of analytics tracking you're using, SessionIDs and so on.

For example:

http://www.CongruentMedia.com
http://CongruentMedia.com
http://CongruentMedia.com/index.cfm
http://www.CongruentMedia.com/index.cfm?TrackingID=TrackWhereThatMugCameFrom

All of these URLs lead to the homepage of our website, but have different formats. The search engines want to provide developers and marketers like us the tools we need to properly tag the sites we want properly indexed so they can better do their job of indexing the pages. To that end, they got together at the local Starbucks and with pen in hand, scribbled down the following code and sent it out to all of the web coders and SEO experts of the world.

Simply put, add this <link> tag to specify your preferred version:

<link rel="canonical" href="http://www.CongruentMedia.com" />

inside the <head> section of the duplicate content URLs:

http://CongruentMedia.com
http://CongruentMedia.com/index.cfm
http://www.CongruentMedia.com/index.cfm?TrackingID=TrackWhereThatMugCameFrom

and the major search engines will all get that the duplicates all refer to the canonical URL: http://www.CongruentMedia.com. Additional URL properties, like PageRank and related signals also make it through.

Google's Webmaster Central Blog does more justice to the nuts and bolts of it all, so I'll turn it over to them if you've got SEO in your blood. Click here to read more.