Sorry, the Delicious tags aren't compatible with the way Firefox tags bookmarks.

I found the solution, Firefox4 and Slurp, works fine.

http://webwanderings.wordpress.com/2011/03/07/importdownload-your-delicious-bookmarks-to-firefox-4-without-loosing-tags/

I recommend Xmarks. For the long-winded reasons why there's nothing better, read below. https://addons.mozilla.org/firefox/addon/xmarks-sync/

1. Once installed, run the setup wizard and sign up for a free Xmarks account.
2. Once signed up, sync your bookmarks.
3. Head over to my.xmarks.com/ and click the Tools menu option on the page, then choose Import Bookmarks From Del.icio.us...
4. Enter your del.icio.us login information so Xmarks can import your bookmarks.
5. You should see a list of your del.icio.us bookmarks. Click the CHECK ALL button, then the IMPORT CHECKED ITEMS button.
6. When Xmarks next syncs your bookmarks, you will have all of your del.icio.us bookmarks complete with tags, in a folder named "Imported from Delicious date of import".
7. If you're the untrusting sort, change your del.icio.us account password.

There are two official Delicious extensions at the moment. "Delicious Bookmarks" which not compatible with Firefox 4.0.x, and "Delicious Extension" which is marked as compatible but doesn't actually work.

@u48998 | Slurp didn't work for me. I got all the prompts like I was supposed to, but clicking the Export button on the delicious page changed its text to Please Wait... and it just got stuck like that with no way to continue. Apart from that, I was rather uneasy about installing an unreviewed extension from an author I've never heard of.

@the-edmeister | You have that backwards. It's Firefox that does not either import or export tags from or to bookmarks.html. The only way to preserve tags when exporting is to create a json backup; these types of files wipe out all existing bookmarks when imported.

Slurp has not been updated to keep up with the Firefox update, besides, the old Delicious is no longer there either. What became of Delicious is obvious by now, it is dead. I have already spent countless hours to get my data out of delicious and I am not going back to Avos.

There's also a problem with Firefox and the way they tag bookmarks. No other browser currently supports their tagging, so if you use Firefox today and have tons of bookmarks with tons of tags, you are SOL if you decide to try Chrome tomorrow. Firefox doesn't even have any updated features for Bookmarks Manager, it is stuck in time since day one.

Overall, personal bookmarks are a major issue for many individuals but no one out there is responsible enough for you to care. I don't wish to trust any third party, so I have not paid attention to XMarks (who knows what they might do to your data in the future). Your locally saved copy of your bookmarks through your browser is the only safe place.

The bugs report for import/export with tags on Firefox.

Export https://bugzilla.mozilla.org/show_bug.cgi?id=423197

Import https://bugzilla.mozilla.org/show_bug.cgi?id=416611