Firefox Add-Ons To Multiple Login

CookieSwap is Add-Ons for the Firefox browser that allows you to easily manage all your cookies, so you can do multiple logins to e-mail accounts like Gmail, Yahoo! Mail, Hotmail or log in to the other as a different user at the same time by using a browser that is Firefox.
If you want to log in using several different ID from the same site without having to log out and then sign in at the site add-ons then CookieSwap can overcome these problems.
For mengunakannya way you can see on the official website.

Homepage : http://cookieswap.mozdev.org/
Download : https://addons.mozilla.org/en-US/firefox/addon/3255