I delete "revsci" but it immediately comes back. How to stop??

In [[Options window|Options]] -> [[Options window - Privacy panel|Privacy]] -> Use Custom settings for History -- Above the 'Show Cookies...' button, you should see one marked 'Exceptions...'. Click that, enter the domain as it appears in the cookies list (eg, ''revsci.net'') and click 'Block'. That should ensure revsci can't set any more cookies. If you delete the cookie now, it shouldn't reappear. For a more aggressive approach, you can [[Disabling third party cookies|Disable third-party cookies]] altogether.