As we all know, Google Panda has penalized many websites with duplicate content over the last few years through its different version releases.
The Google Panda update will always penalize those websites where it will find duplicate content. Now, it doesn’t matter whether that duplicate content was created intentionally by the webmasters or created automatically by the CMS software.
In my experience as an SEO Consultant, I have often observed that most CMS software would create multiple URLs for a single page because of the system format it has been built upon. E.g., an e-Commerce CMS may show a webpage with product details through multiple URLs like the below:
http://websitename.com/product.php?id=590
http://websitename.com/product-name/
http://websitename.com/category/product-name/
It is worth noting that all the URLs in the above example display the same page and information. Let me add that search engines, especially Google, consider multiple versions of the page to be duplicate content.
To avoid such a penalty, you must ensure that a particular tag is used on every page of your website. This specific tag is known as the ‘rel canonical’ tag. The ‘rel canonical’ tag informs search engine spiders about the original version of a webpage. So, you can choose the desired URL version for every specific web page and use it with a ‘rel canonical’ tag so that Google can consider it a ‘true’ version of the original webpage. E.g., to fix the problem in the criteria mentioned above, we could use the ‘rel canonical’ tag as below:
<link rel=”canonical” href=”http://websitename.com/product-name/” >
This script must be included on every website page before the </head> tag. Again, if you are unsure how to use this script, you may seek advice from your SEO Consultant or contact your web developer to do this for you.