Firefox users who have outdated versions of the most popular plugins will soon see a notification urging them to update when they visit a web page that uses them. Old versions of Silverlight, Adobe Reader and Adobe Flash on Windows are covered by this.
While you are free to ignore the warnings and continue using your old plugins, we strongly recommend that you go to our Plugin Check page and update them as soon as possible. Old plugin versions can cause stability problems and are potentially insecure. Keeping them up to date will ensure that you have a great Firefox experience.