Keep until: they expire: Each cookie will be removed when it reaches its expiration date, which is set by the site that sent the cookie. I close Firefox: The cookies that are stored on your computer will be removed when Firefox is closed. ask me every time: Displays an alert every time a website tries to send a cookie, and asks you whether or not you want to store it.
Close the about:preferences page. Any changes you've made will automatically be saved.