Backup your Firefox's Bookmarks now. There is one built-in feature to backup Firefox's Bookmarks. Check this out.

1). Select 'Manage Bookmarks' or In Firefox 3 Beta select 'Show All Bookmarks' (in Firefox 3 beta) from 'Bookmarks' menu

Manage Bookmarks in Firefox version 2. . . and Below	Show All Bookmarks in Firefox 3 Beta

2). Go to 'File' menu and select 'Export' in Bookmark Manager or In Firefox 3 Beta Select 'Import and Backup' (in Firefox 3 beta) in
Library.

Export option in Firefox version 2. . . and Below	'Import and Backup' in Firefox 3 beta

3). Select 'Export' option or In Firefox 3 Beta select 'Backup' option (in Firefox 3 beta)

4). Enter a Bookmark backup filename. e.g: "Bookmarks 2008-03-31.html" and save