It appears straight out WordPress installation needs to be prepped up for Google’s policy on duplicate content. I notice that I showed up in Google search results on the top pages for particular keywords but suddenly all results for the same keywords just dropped out of Google’s search results. Reason behind is because of the duplicate content in the WordPress post that is being picked up by the googlebots.
Nice post about this issue here Problems With WordPress Posts Going Supplemental In Googleâ€™s Index. And found a solution by downloading this plugin here All In One SEO Pack.