First, you will need to ensure that Firefox is setup to remember your passwords. To do so, please follow these steps:

1. Open the Firefox options
2. Select the Security section from the sidebar
3. Ensure that Remember logins for sites is checked
4. Press the Exceptions... button next to the Remember logins for sites setting
5. This list contains websites that are told not to save the password, so you will need to remove any websites from this list that you want to save passwords on or press the Remove All button to clear the list

Next, you will need to ensure Firefox is allowed to save your form history. To do so, please follow these steps:

1. Open the Firefox options
2. Select the Privacy section in the sidebar
3. Select the Remember history from the History drop-down menu or ensure that Remember search and form history is checked if the drop-down menu is set to Use custom settings for history

Note: Some website may prevent you from saving passwords and/or usernames as an added security measure. Therefore, this feature may not function properly on all websites.

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:

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Tools > Options > Privacy > "Use custom settings for history" > Cookies: Exceptions

Removing cookies from a website makes the website forget about you.

Make sure that you do not run Firefox in permanent Private Browsing mode (Always use Private Browsing mode; never remember history).

• https://support.mozilla.org/kb/Private+Browsing

• Tools > Options > Privacy > Firefox will: "Use custom settings for history"
• Deselect: [ ] "Always use Private Browsing mode"