I've been seeing that today too. My guess is that soon we'll see a reply on this thread to the effect "problem fixed, do a hard refresh by pressing ctrl-R" :-)
It's a game alert for a game I've already moved in. Typically it's an alert I got recently (within 10-30 minutes probably) that I've already responded to. It's like the alert is stuck in the system and won't go away even if I click on "view".
The problem has gone away. I was getting the alert box to appear on my home page and any other page I visited saying I had a tournament game ready for my move even though I had just made a move, I visited multiple pages after I had made the move and refreshed pages as well. I visited the game page and it was not my turn to move.
I have an alert that is popping up on my home page and it is not my turn to move, any reason this might be happening?