Firefox now supports tagging for bookmarks. Want to use your del.icio.us bookmarks in Firefox 3? Follow these simple steps:
Log into del.icio.us and go to settings > export/backup
Make sure the include tags box is checked, and click export to HTML
In Firefox click on Bookmarks > Organize bookmarks
Click on the 3rd icon at the top of the window and select Backup…
Upload the files you created in steps 1 and 2 here:
In Firefox click on Bookmarks > Organize bookmarks
Click on the 3rd icon at the top and select Restore > Choose file
Select the file you just downloaded from step 3