An agreement was struck yesterday by the three main search engines (Google, Yahoo and MSN) on the adoption of a new tag to tackle canonicalisation in the SERPs.Canonicalisation is the challenge of having multiple pages of the same page due to outdated software such as a content management system or forum. Examples of pages that out put duplicate content include:
- Having the same content on the www and non www versions of your homepage or internal folders.
- Printer-friendly pages
- Forum threads with session id’s
An example of the new canonical tag which is placed in the HEAD of the page (where Title and Meta Description tags are placed) looks like this:
<link rel="canonical" href=http://www.yoursite.com/forum>
By placing the above tag in the <head> of pages with similar content, you would inform search engines that the page is a copy of the URL www.yoursite.com/forum and that all popularity and strength of any other duplicate pages should be passed on to that URL.
Previously, canonicalisation was addressed through rules placed in the .htaccess file of a domain. This tag while more manual, is much easier to understand by less techie webmasters and is a fantastic development on the part of search engines.
Official announcements by the three search engines can be found here: