On my Yahoo! mail, the folder list says I have 1 unread message in my inbox, but when I go to my inbox I’ve read everything. I’ve logged out and back in again, still there.

Hmm.

Update: It’s now happening in other folders. Looks like a bug at Yahoo! in the database. That or there are a bunch of messages I thought I read but didn’t because they won’t show up. Oh well.