Not entirely sure why this requires a Firefox account. It appears possible to install the mentioned add-ons manually:<p>Tab Center appears to be available from <a href="http:&#x2F;&#x2F;people.mozilla.org&#x2F;~bwinton&#x2F;TabCenter&#x2F;" rel="nofollow">http:&#x2F;&#x2F;people.mozilla.org&#x2F;~bwinton&#x2F;TabCenter&#x2F;</a><p>Universal search: (edit: link here was incorrect)<p>Activity streams: <a href="https:&#x2F;&#x2F;moz-activity-streams.s3.amazonaws.com&#x2F;dist&#x2F;latest.html" rel="nofollow">https:&#x2F;&#x2F;moz-activity-streams.s3.amazonaws.com&#x2F;dist&#x2F;latest.ht...</a>