Since Firefox 3 was first released to the public in alpha status, many have enjoyed the new bookmark tagging feature which allows you to not only bookmark your favorite sites but also organize them using tags like many modern online bookmarking services. In fact, this new feature has even given people the desire to migrate their existing data from the del.icio.us bookmarking service into Firefox.
Delicious allows you to export your bookmarks to an HTML file and while the file does include your various tags, Firefox 3 does not allow tags to be imported via an HTML file. Instead, the browser uses the .json data interchange format to deal with tags. So, up until now, I’ve been able import my del.icio.us bookmarks into Firefox via HTML but the many different tags I’ve assigned using the del.icio.us service were NOT imported.
Fortunately, the latest release of Flock, the social browser we’ve covered before, can act as a transition tool to allow for the type of import you want. Flock, by default, automatically merges del.icio.us bookmarks with your own local bookmarks (including tags) when you engage one of Flock’s "social" features and login to the Delicious service.
Now, as you may have read, the Flock 2.0 beta was released today. This release finally uses the Firefox 3 code-base thus enabling Flock to use the same bookmarking system (for the most part) as Firefox. So, if you enable the Delicious service from within Flock 2.0, you can then export your bookmarks to a .json file once Flock has finished integrating them with your local bookmarks. (Note, this can take more than a few hours depending on the amount of bookmarks you have stored on the del.icio.us service.) To do this, open up the Favorites Library by going to Favorites > Organize Bookmarks from within Flock 2.0. (You’ll notice an interface similar to that of the Firefox 3 bookmarks library.)
From there, select the "Import and Backup" option from the main menu and save the .json file to any directory you’d like.
Now, open up Firefox 3 and head over to Bookmarks > Organize Bookmarks. From the main menu, select Import & Backup > Restore > File:

Find the .json file in your file explorer and import the contents. Once Firefox is finished importing your bookmarks, the tags section over in the navigation area will now contain the entire list of tags you’ve created/assigned through del.icio.us:

Now, normally in Firefox 3 or Flock, you could click on one of those tags and any bookmarks related to that tag would then be displayed over in the left-hand side. What’s strange, and something I’ve yet to figure out, is that the bookmarks DON’T display in the area on the left when selecting a tag in the nav area. However, when you type in a tag or a keyword relating to a site you’ve bookmarked from inside the location bar (a.k.a. "awesomebar" or "address bar") in the main Firefox window, the appropriate results display:

Regardless, your favorite sites are now discoverable from within Firefox even if the situation isn’t 100% conventional. You should also note that, with this scenario, an HTML export of your bookmarks from within Firefox doesn’t perform properly. A .json export and restore (like we did above) does, however, work properly but you end up with the exact same result…no visible bookmarks in the Bookmarks Manager.
Anyway, it’s a temporary solution if you’re wanting to migrate your data. If you have any other suggestions or solutions, feel free to contact us (suggest *at* fansoftech *dot* com) or drop a comment below.
Update: the fine individuals at e-accent.com have created a site dedicated to this very idea: http://delicious.e-accent.com.

Basically, you backup your current bookmarks from Firefox (to the .json format.) Then, you export your current bookmarks from http://del.icio.us (with tags). Once you have those two files, you can merge them together with e-accent’s tool and the site will generate a .json file that you simply import into Firefox 3.
It worked like a charm for me but I did notice that I needed to un-check the "notes" option when exporting from the Delicious site in order for the e-accent tool to generate a proper merged .json file. Now, I have all of my del.icio.us bookmarks WITH tags inside Firefox.
I’ll now be using Mozilla’s Weave Firefox add-on to synchronize these bookmarks with my other machines. I’m already using Weave to synchronize browser cookies and passwords so this conversion just allows me to rid myself of one extra extension that I have to keep up with when re-installing Firefox on any of my machines.