Many people store their password in their browser so they dont have to type it in. if you have done this and then later on forgotten your password, you can obtain the stored password from your browser using the instructions below.
Also – if your password is changed, then you can also use the below instructions to change the stored password.
Tutorial with screenshots on VasudevaServer.org: Changing stored passwords Firefox at Vasudeva Server.org
To retrieve passwords, you will need an application called IE PassView. You can download it from http://www.nirsoft.net/utils/internet_explorer_password.html by scrolling to the bottom of the page.
In order to start using it, just run the executable file (iepv.exe). After running iepv.exe, IE PassView scans all Internet Explorer passwords in your system, and displays them in the main window.
Full tutorial: View stored passwords IE
Safari and Google Chrome (Mac)
You can see passwords by opening the Keychain Access program (Applications >> Utilties >> Keychain access). You will then see a list of all saved passwords on your computer.
Navigate to the website or username whose password you forgot and doubleclick. Check the ‘show password’ checkbox to see the password.
Full tutorial: Manage Passwords Safari
Google Chrome (Windows)
There is a tutorial here: http://www.threetipsaday.com/2008/12/recover-saved-passwords-google-chrome/