The first few times I saw this, I thought I was just mistaken.. but it's happened so many times now I know it's not me, this is really happening: older Firefox pages reappear if I Alt-TAB away and then return to Firefox.
It's Gmail where I can most easily notice this, so it MAY have something to do with Ajax, but I THINK I've seen it on other pages too (confirmed: I just saw it on another page). It's pretty weird: let's say I've opened up in the morning to twenty unread Gmail messages. I read and delete 15 of them, then Alt-TAB off to do something else.. but when I come back, the messages I read or deleted show up as though I had never touched them. They really aren't: a "refresh" shows the correct view instantly, but it's quite confusing.
I know, you probably think I'm nuts - or have two Gmail windows open. It's definitely not the latter, and I don't think that taking my wife's appraisal of my mental state is valid. Really: this happens.
It MAY have something to do with Parallels: it seems like it happens more often if I've Alt-TABbed there.. but it's not repeatable - I've not found anyway to demonstrate this consistently.
Anybody else ever seen this? It might have something to do with running the Firefox 3 Beta too - I'm not sure if this started just after loading that..