As we all know that Google Panda has penalized many websites which had duplicate content many times through its different version releases during last few years.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 it was created automatically by the CMS software.
In my experience as SEO Consultant, I have often observed that most of the CMS softwares would create multiple URLs for a single page because of the system format it has been built upon.For eg. an e-Commerce CMS may show a webpage with product details through multiple URLs like below:
There is one thing worth to note here that all the URLs in above example would display the same page and same information.And let me add here that these multiple versions of the page are considered as duplicate content by search engines especially Google.
In order to avoid such a penalty,you must ensure that a special tag is used on every page or your website.This special tag is known as ‘rel canonical’ tag.The ‘rel canonical’ tag informs search engines spiders about the original version of a webpage.So,you can choose the desired version of URL for every specific web page and use them with ‘rel canonical’ tag so that Google can consider it as a ‘true’ version of original webpage. For eg. in order to fix the problem in above mentioned criteria,we could use ‘rel canonical’ tag as below:
<link rel=”canonical” href=”http://websitename.com/product-name/” >
This script has to be included on every page on your website before the </head> tag.Again,if you are not sure how to use this script,you may seek advice of your SEO Consultant or you may contact your web developer to do this for you.