Today Google has shut down the ‘Blocked Sites’ feature that allows you to block domains and hosts to appear on search results page. But its not a big problem because you can simply switch to Personal Blocklist (by Google), an official Google Chrome Extension that allows to block particular sites from Google search results. You can download your existing Blocked Sites list as a text file from Google and make use of it in this extension.
Personal Blocklist (by Google) will transmit to Google the patterns that you choose to block and when you choose to block or unblock a pattern, the extension will also transmit to Google the URL of the web page on which the blocked or unblocked search results are displayed.