If your website suddenly lost all rankings on Google it was once listed for, you might have been blacklisted (sandboxed) as a spammer by Google. Not to worry and panic. There are steps you can follow to get your website restored. Google and other search engines usually penalizes websites that follow black hat SEO techniques. Black hat SEO usually includes link farms, paid links and selling text ads. If you fix all the problems on your website (removing all the black hat SEO stuff), chances are good that you can submit a Google Reconsideration Request through to them to get your website listed again.
View below a YouTube video by Google where they explain the steps for “requesting reconsideration using Google webmaster tools”.
Check for access issues
On the overview page once you have logged into Google Webmaster Tools and selected a domain, you can view the last date that the Googlebot successfully spidered your website. On this page you can also view any crawling errors that the bot encountered while crawling the selected domain. These errors usually include pages not found, unreachable URL’s, timed out errors, URL restrictictions, xml sitemap errors, restrictions by the robots.txt file and HTTP errors.
Check for messages
Check on the message center of your Google Webmaster Tools account for any messages Google has sent you regarding the errors of your website.
Google Webmasters Guidelines
If there’s no messages regarding your website and no errors on the overview page, have a look at the Webmaster Guidelines by Google to see if your site is or has at some point been in violation with their guidelines.
Fix your website
If your website is in violation with their guidelines as explained above, make the necessary fixes on your website so that it falls within their Webmaster Guidelines.
Submit a reconsideration request
Once logged in to your Webmaster Tools account click on tools, “Request Consideration”. Explain what you think was wrong with your site and what steps you have taken to fix it. You will receive a message in the Message Center confirming that Google received your request.