On step 4, AddRoundKey, shouldn't e5+17 be fc, not f2? Or is AES using something other than simple 8-bit modular arithmetic? It looks like the author did the arithmetic in his/her head, and accidentally used decimal for the second digit (5 + 7 = 12, mod 10 = 2).
That's what I get for learning programming years before entering college. I forget standard mathematical notation, since I always use programming language operators (like ^) in my head. Further, I only checked the first row to make sure it was actual addition, and obviously 0xa0 + 0x04 == 0xa0 ^ 0x04.
