Google Browser Sync

Google Browser Sync for Firefox is an extension that continuously synchronizes your browser settings - including bookmarks, history, persistent cookies, and saved passwords - across your computers. It also allows you to restore open tabs and windows across different machines and browser sessions.
Please note: Google Browser Sync must update your browser settings whenever you start Firefox. This will increase the start-up time of Firefox (the time between clicking on the Firefox icon and loading your start page) - please bear with us as we work to decrease this delay.

How to Use
To use Google Browser Sync, simply install and configure the extension on all computers for which you'd like your browser settings automatically kept in sync. Even if you only install Browser Sync on a single computer, you can use it to backup your browser settings and to restore your open tabs and windows across browser sessions.

Configuring your computers
After successfully downloading and installing the extension, then restarting your browser, you'll see a setup wizard. (Please note that you'll need a Google Account to complete the setup process; if you don't already have a Google Account, you can create one now.) The setup wizard will take you through a series of quick and easy steps. You'll need to choose which browser components you'd like to keep synchronized with your other computers (the standard install includes all possible components), and choose a PIN to protect your sensitive information.
Configuring your second computer is even easier. You only need to install the extension, log in with your Google Account username and password, and provide your PIN.

Day-to-day use
Google Browser Sync is completely automated. The settings you select at startup are automatically synchronized across each of the computers on which you install Browser Sync. You won't even need to log in every time you start the browser. You can change which browser components are being synced - or even stop the syncing process entirely - using the settings panel in the upper-right corner of the page. The settings panel also gives you access to your PIN. How to Uninstall In the Firefox browser, click "Tools" and select "Extensions". The Extensions window should appear. Click "Google Browser Sync", then click the "Uninstall" button. Click the "OK" button in the confirmation window. The Extensions window should confirm that Google Browser Sync has been uninstalled. Close the Extensions window, then close all Firefox windows and restart the browser.

link:
http://www.google.com/tools/firefox/browsersync/index.html