Box.net Bookmarks Synchronizer
Box.net Bookmarks Synchronizer is a Firefox Extension.
You can download it from the Firefox Add-Ons site.
Box.net is an online file storage/sharing service.
This extension can be used to backup your Firefox bookmarks to your Box.net account. You can even sychronize the bookmarks between multiple computers.
To backup your bookmarks, just go to the top of your browser and click Bookmarks > Box.net Backup:

In the “Main” tab, enter your Box.net account information (i.e., e-mail & password).
Then click the “Save” button:

Your bookmarks have now been backed up.
Your Box.net account will look like the screenshot below:

Let’s go back to the window where you had to input your Box.net account info.
Clicking on the “Advanced” tab will give you the following options:

As you can see, you can automatically download your bookmarks file from Box.net when you open Firefox.
You can also automatically upload your bookmarks to Box.net when you close Firefox.
Making use of these options will keep your bookmarks in sync on multiple computers (provided you have this extension installed on both machines).
Finally, here is the “Help” tab:
















