What is the duplicate content penalty? If you have content on your site that google knows is the same as content on another site then it may penalize you for it. Contrary to popular belief you will not be dropped from google for doing this (unless its on a very large scale). The penalty simply means that you will not feature in a search featuring any of duplicate content. How to check whether the penalty is being applied? Find text string from some text you know is listed on more than one website and search for it in google. Hopefully the original site will be listed first and the sites that copied the content will not rank. Next do the same search but add inverted commas around the search term. Any sites that were held back by the penalty in the first search will show up on this second search. Example This search shows an article from ezinearticles at number one with no other sites showing an exact match. This search shows seosubmit.com possibly suffering from some kind of penalty from having the same content as ezinearticles. Disclaimer: I am not saying any of these sites have copied content or done anything wrong - this is just the first example I found. If anyone has any comments on this theory or more examples to illustrate what is going on here please post them.