What you need to know

You can easily clear the usernames and passwords that Firefox has saved for you. Note: These steps apply to Firefox for Windows, Linux and Mac OS X.

1. In Firefox, click the Menu  button located at the upper-right corner of the window, then choose Options.
2. Click Privacy & Security on the left pane.
3. Click the Saved Logins… button.
4. To delete individual site passwords, select the website, click on Show Passwords, select the one to delete, then click Remove.
5. To delete all saved passwords, select the website, then click Remove All.
6. When you’re done, click Close.
   
   
7. If you want Firefox to no longer remember passwords in the future, uncheck the Remember logins for sites option.