del.icio.us Bookmarks

Hmm... I started a del.icio.us account today, and am trying to get my head around using and organising it all. Maybe it wasn't a good idea to import all of my bookmarks... there was over 1000 of them, and doubtless most of them are crap. So I'm going to figure out the best way to clean them up...
and do they stay in synch with my Firefox bookmarks? Or should I just clean them up on del.icio.us and them import them into Firefox? Or vice versa, maybe?
Such dec.isio.ns...