I'm going to move my Firefox 4 bookmarks to another computer. How should I move them without losing any custom folders and locations for the bookmarks?
You can manually save your bookmarks in a single
.json file, and later on use that file to restore them.
On the Menu bar of Firefox 4, click on the Bookmarks tab and then click on "Show all Bookmarks" from the dropdownlist. In the Library window thus opened, click on Import and Backup tab, and select "Backup...". Give a name to your file and save it to an external drive or an online drive.
If you always want your bookmarks to be synced or saved on the cloud, follow @Sathya's solution.
You can also try MozBackup http://mozbackup.jasnapaka.com/download.php It can backup all your profiles:
MozBackup is a simple utility for creating backups of Mozilla Firefox, Mozilla Thunderbird, Mozilla Sunbird, Flock, SeaMonkey, Mozilla Suite, Spicebird, Songbird and Netscape profiles.