Firefox has a functionality to save your password,and we use the saved password so often that we may forgot the password.
This brief tutorial may help you when you’ll login to the websites by entering password for any reason.
In a firefox window click to go to Edit–>Preferences,then select Security tab(Tools–>Options,Privacy tab in windows).
Click on Saved Passwords..,and type in Search field or select directly the website you want to login,then click Show Passwords button.
Select Passwords tab,then click on the View Saved Passwords,scroll down to select the website at the next window and click on Show Passwords at last.