Duplication of content- recipe for disaster.

Over the last couple of weeks we have had three clients all with duplication issues that have impacted their rankings in Google.

In February 2003 Google registered a new patent for technology for
identifying duplicate pages, and more importantly, near duplicate pages.
This technology is intended to address web spam, where copy is taken and
reused multiple times, just changing the odd word or phrase to change the
emphasis and hence the optimisation. However completely legitimate uses have
also incurred a penalty with regard to this filter.

There is something referred to as "canonical domains" where content is hosted on http://www.domain.com but because of how a server is set up it also exists on http://domain.com. A CNAME record or canonical name record makes one domain and alias of another. This is not actually a problem until you start getting your domain known, because if Google has not visited the non www (CNAME)
version there is no impact on your sites listing.

However as two clients recently found out when they moved servers, if the canonical domain issue is not dealt with the transfer, rankings can plummet dramatically. Prior to the domains being moved both clients enjoyed a top 5 place for their chosen keyphrases.

It is a comparatively easy process to fix, there are 3 options - disable the canonical to bring up an error page, redirect using a 301 to the preferred page or place different content on the page for manual redirection. But ultimately having duplicate content or near duplicate content should be avoided at all cost. In the cases of the recent clients, on correcting the situation the sites returned to their previous ranking almost overnight.

M.P

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