Canonical Linking

Duplicate Content Can Pinch Your SEO Efforts

Not only can duplicated content make it difficult for search engines to index your web pages properly, but it can lead to penalties that could dramatically effect a website’s ability to rank well for targeted keyphrases in the major search engines.

As websites grow-up, the potential for duplicate content increases. Sites that contain a lot of content might have a variety of different URLs that all reference the same location. This issue can often impact smaller websites that show up in search engine results with and without the ‘www’ in front of the corresponding URL.
An Open Standard Solution Supported by Google - Yahoo! - and Microsoft

Even though Google Webmaster Tools has an option to select the ‘www’ preference for the URLs of your website, a tactic with more control that is acceptable for other search engines was needed. The canonical link element was developed to help search engines determine the preferred URL to be used for your website.

When linking to pages of your site or blog, utilize the canonical link element in the header portion of your links.

Here’s the canonical link element in action:



This tells the search engines that the prefferred URL is http://example.com/page.html (note: without the ‘www’). Where canonical = preferred.