What does this message mean?
 

Often, I get this message when I click on a link (I got 3 today):


vBulletin Message
Invalid Thread specified. If you followed a valid link, please notify the administrator

I'll be watching this as I'm getting the same message.

An Invalid Thread is one that has either been:
-moved and the redirect has expired;
-merged and the redirect has expired; or
-deleted because it did not comply with policy

A closed thread is one that remains visible but can’t have new comments added.