In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.

Are you using sync?

Type about:preferences#security<enter> in the address bar.

Under Logins, Turn on Remember Logins. To check the passwords you have listed, press Saved Logins.

Note that a detail like a website remembering you (log you in automatically) is stored in a cookie.

You can use these steps to make a website recognize and remember you:

• you can create an "Allow" exception to keep specific cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: Exceptions

Let the cookies expire when Firefox is closed to make them session cookies instead of using "Clear history when Firefox closes" to clear the cookies.

• Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: Keep until: "I close Firefox"

You can create an "Allow" exception to keep specific cookies.

In case you use "Clear history when Firefox closes" or otherwise clear history.

• do not clear the Cookies
• do not clear the Site Preferences

• Options/Preferences -> Privacy -> Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" -> Settings
• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

• clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data
• clearing "Cookies" will remove all selected cookies including cookies with an "Allow" exception you may want to keep

If you have a problem with the Password Manager then check for issues with the logins.json and key3.db files in the profile folder.

• https://support.mozilla.org/en-US/kb/Profiles
• http://kb.mozillazine.org/Profile_folder_-_Firefox