''locking this thread as duplicate, please continue at [https://support.mozilla.org/en-US/questions/1092721 /questions/1092721]'' The latest version of firefox has installed itself on my PC. I like my cookies window open, so I went to about:config in order to change the "browser:prefernces:incontent" string to "false", but it was already set to "false". So I clicked on "reset", which seems to have been a mistake, because now "browser.preferences.incontent" is not even in the list anymore. I'm not sure what I've done or how to get it back. Thank you.