I'm a bit surprised IE complains about it, but it's a good thing it does: You're missing a declaration in getPage for hash (e.g., put var in front of the first use).
On the others it's presumably creating an implicit global (a property of the window object called hash), which is of course a Bad Thing(tm), but as I understand it it's correct according to the specification (the relevant sections being 8.7 ["The Reference Type"] and 10.1.4 ["Scope Chain and Identifier Resolution"]).
Still surprised IE is complaining about it, though. It must have to do with the scope in which jQuery is calling your click handler.