Add-on for blocking sites in Google Search

Firefox userscript

What I ended up using is this script for GreaseMonkey: https://greasyfork.org/scripts/1682-google-hit-hider-by-domain-search-filter-block-sites

You first need to install the GreaseMonkey extension and then install the script: https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/

Once installed, you can easily add blocked sites to your list, clicking directly on the "Block" button which appears next to each Google search result.

You can use Google's Personal Blocklist extension for Chrome which allows you to block certain domains from showing up in Google Search results.

The personal blocklist extension will transmit to Google the patterns that you choose to block. 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.

optimize google firefox add on does this task for Firefox