Warning! If you are in Venice they will be glad to sell you a museum ticket for 4 museums around St Mark's Square. The catch is that they closed the separate entrance to the Archeological museum and you must enter it through the Correr museum. The problem is they will only let you enter each museum once. They would not let us into the Archeological museum because we saw the Correr museum the day before.
The Archeological museum is listed as as separate museum, but that certainly didn't matter to the staff.
I have complained to the museum network. Hopefully they will fix the situation. Their attitude seems to be very unprofessional since they list the Archeological museum as a separate entity.