Here's when Firefox 4 tells Flash Player version 10.3 to delete LSOs (Flash cookies):
- When you clear all your cookies in Firefox using "clear recent history" [how-to link]
- When you choose "forget about this site" in your library (history) window [how-to link]
- When you quit Firefox, if you have Firefox configured to clear your cookies automatically upon exit [how-to link]
Chrome and Internet Explorer are also supporting this behavior, so this is fantastic news for everyone's privacy on the web!
More reading for techies: