Disable HTML 5 Video Autoplay
By default, Firefox plays HTML 5 videos once they're loaded in a page, which is particularly annoying. To turn this off, do the following:
- Type about:config in the browser's address bar and hit enter.
- Confirm that you will be careful if the notification comes up.
- In the Search: box, type media.autoplay.enabled to filter to the setting.
- Double-click the setting so that its Value column reads false.
- Close the about:config tab.
Won't Prompt to Remembers Passwords
Click Tools, choose Options. Under the Privacy tab, in the History frame, under Always use private browsing mode, make sure that Remember search and form history is turned on.
Won't Stay Logged In
Click Tools, choose Options. Under the Privacy tab, in the History frame, click the Settings button next to Clear history when Firefox closes. Make sure "Active Logins" and "Cookies" are unchecked in the History frame.