People tend to spend a lot of time building their site making sure that it looks perfect, aesthetically. Then they spend many hours going through doing on-site optimization to make sure it’s ‘aesthetically’ pleasing to the search crawlers. THEN, you spend more time creating links to the site to help it rank. But so often people do all of these things and forget to make sure that their site doesn’t have duplicate content.
Duplicate content can range anywhere from redundant pages (www.domain.com and www.domain.com/index.html) to actual duplicate content (recycling posts on multiple pages) to duplicate content in meta data (redundant meta tags, titles, and descriptions).
https://www.google.com/webmasters/tools/home?hl=en – This is a great tool that Google has created to help webmasters run their sites. Within in this ‘toolbox’ there is a tool that goes through and scans for duplicate meta data. It will highlight the issues to you so you can quickly find and remedy the issue.
http://www.webconfs.com/similar-page-checker.php – This is another tool you can use to determine if you have duplicate content or content that is more than 70% similar on the front end of your website. If it is more than 70% similar then Google will decide that it is duplicate and will penalize you.
Now that you have found the content make sure to go through and clean it up pronto so that you will be good to go the next time you get the all important crawl. Make sure you have new content added to the site often so that the crawler will come through more often so as you make these minor improvement your position will go up.