Firefox Private Data

Windows

This is how to reset current versions Firefox:

1. Click on the icon in the upper right hand corner of the browser that looks like books on a bookshelf.
2. Click on History
3. Click on Clear Recent History...
4. Set the "Time range to clear" to Everything and ensure that the Cookies, Cache, and Active Logins checkboxes are checked off. You may also check off Browsing & Download History, and Form & Search History if you desire.
5. Click on Clear Now. Close Firefox, open it back up and you're good to go.

Hitting CTRL+SHIFT+DEL will sometimes take you right to step 5, but it does not always work.

Mac

Firefox 3.5 and above for Mac

You can clear your Firefox cache, cookies, and history by:

1. Pressing command+shift+delete at the same time.
2. Here you can choose to delete cache, cookies, and history. Usually you will only need cache and cookies.