Google is really maximizing their datacenter warehouses to provide better user experience while using Google Chrome browser by introducing a new Google Chrome Extension called Personal Blocklist.
What does it do? Basically it will enables users to block websites from Google's search result which doesn't fit to his search and this will be given as feedback or input to Google to refine their search results. In other words, Google is using their users feedback to improve their algorithm and search results. Clever thing right? . Every link on the search results will have an addition of link on the bottom which is added by the extension to block the site.
You can revoke the website you previously removed by clicking the Show link on the bottom of the search results and click on the unblock on the side of the link.