As far as I know, theres only a type I and II...
maybe you are referring to the CF Extreme III and IV cards produced by scandisk.
Those are just product names and do not refer to compability.
The Digital Rebel XTi (or D400) can handle CF type I and II Cards.
Peter
PS: if you refer to the CF-Standarts of 2.0, 3.0, 4.0 I cant actually give you an answer