Bolle and Bunsen have the right answer.
USB 2.0 "High Speed" will only be possible in OS X 10.2 or higher. (I think it's 10.2.6 specifically, but I might be wrong on that one, and it's even possible that there is a hack that lets it work in 10.1.) In OS X 10.0, 10.1 (from what I recall,) or OS 8.1 to 9.2.2, any USB card that works will operate at USB 1.1 "Low" or "Full" speed. Before OS 8.1, USB isn't possible at all. (I seem to recall a hack that made it work in 8.0, but I can't find any reference to it now, and I know it won't work in 7.x.)
USB 2.0 "High Speed" will only be possible in OS X 10.2 or higher. (I think it's 10.2.6 specifically, but I might be wrong on that one, and it's even possible that there is a hack that lets it work in 10.1.) In OS X 10.0, 10.1 (from what I recall,) or OS 8.1 to 9.2.2, any USB card that works will operate at USB 1.1 "Low" or "Full" speed. Before OS 8.1, USB isn't possible at all. (I seem to recall a hack that made it work in 8.0, but I can't find any reference to it now, and I know it won't work in 7.x.)