In Mozilla Firefox, there is the ability to save passwords automatically, for the sites you access. In the Firefox options, you are able to view all of your saved passwords.

If your computer got stolen, or hacked, there is a chance the hacker/thief will look in to your saved passwords, and steal private data from you, or steal your accounts on social networking sites.

Setting a Master Password helps ensure that you need a password to access all of your saved passwords.

Once per session (which means, you open Firefox for the first time, after an exit, or restart of Firefox), Firefox will ask for the Master Password before you can allow Firefox to automatically fill your password in a site, or show you the saved passwords.

To set a Master Password in Firefox, click Tools > Options

then, click on the Security tab.

Place a check in the box next to Use a Master Password. A screen will launch. It will prompt for you to enter the password twice. Once you have set the password, exit Firefox.

Then, restart Firefox. You should be prompted to enter that Master Password every time you want to see the Saved passwords, and once when you access a page that a password should be filled by Firefox.