Request Reconsideration of Your Site: Google Webmaster Tool

Google is great and it gives you a chance to rectify your flaws for websites and states onits page and same is as quoted below:
If your site isn't appearing in Google search results, or it's performing more poorly than it once did (and you believe that it does not violate our webmaster guidelines), you can ask Google to reconsider your site.
One can get website reconsideration form for Google here.