When the back arrow doesn't take you where you were, what does it mean and how else do you get there?

In Fluther about an hour ago, I tried to use the back arrow to get to the list of things that have to do with ”..cookies, leaving .. logged in…” but it was no longer there. Have you read it?
When the back arrow doesn’t take you where you were, generally, what does it mean and how else do you find it? I wrote the moderator about the Fluther part, but I need an answer for the general question.