When you block a site with the extension, you won’t see results from that domain again in your Google search results. You can always revoke a blocked site at the bottom of the search results, so it's easy to undo blocks:
You can also edit your list of blocked sites by clicking on the extension's icon in the top right of the Chrome window.
This is an early test, but the extension is available in English, French, German, Italian, Portuguese, Russian, Spanish and Turkish. We hope this extension improves your search experience, and thanks in advance for participating in this experiment. If you’re a tech-savvy Chrome user, please download and try the Personal Blocklist extension today. Posted by Matt Cutts, Principal Engineer