A few weeks (months?) ago I noticed that the del.icio.us login page would no longer get auto-filled with my saved username/password information in Firefox. This is presumably Yahoo trying to be uber-secure, but for me, it’s just an annoyance … my Firefox passwords are secured by a Master Password, and having the fields autocomplete just saves me time every morning when I get online. Luckly, Elliotte Rusty Harold had noticed this mis-feature too, and has found a solution to get del.icio.us to accept the passwords remembered by Firefox. Be sure to read the comments to his post, since his helpful readers have provided several solutions … take your pick !
The easiest way I found was this Greasemonkey script which turns off autocomplete for all sites. You can change the site list to only include http*://*.del.icio.us/* if you want.