ownCloud 6 comes with a fantastic Mozilla Sync option that allows you to synchronise your Firefox bookmarks and other settings with your ownCloud instance rather than using Mozilla or another less credible third party provider. This is how I set it up:

In your ownCloud Instance:

Mozilla sync in ownCloud

In Firefox on Your Desktop

If you entered your credentials correctly, you should be returned to the Sync tab in Firefox preferences.

Firefox ownCloud Sync Success

Enjoy syncing Firefox to your own cloud :-)