If you share your computer with other people, you may want to prevent them from logging in to your social network account, viewing your stored passwords and changing your bookmarks in Firefox. This article describes basic protections to take.
You should create individual user accounts for each person who regularly uses your computer. This allows each user to have his or her own customization such as the wallpaper and visual style, and his or her own document folders such as the Firefox profile that stores your form history, Internet usernames and passwords, bookmarks, and other personal settings. Each person accesses his or her user account with a username and password.
To create a user account:
For more information on choosing secure passwords, see Create secure passwords to keep your identity safe.
When you leave your computer, you should lock the screen to prevent other people from using your desktop and accessing your files. You will still be logged in and all your applications will keep running, but you will have to enter your password to use your computer again. You can lock the screen manually, but you can also have the screen lock automatically.
In case someone would access Firefox if you forgot to lock your computer, you can also set a Firefox master password. For more information, see Use a Master Password to protect stored logins and passwords.