First of all, I just implemented AES because I wanted to understand how it works and as a challenge to see if I could do it and I won't use to encrypt anything important, ever.
The (German) Wikipedia article of AES linked to a flash animation which demonstrated precisely how AES-128 in ECB mode worked. I implemented AES exactly as shown in that animation and I am able to reproduce the same encrypted byte array they get in the result.
In that example the hex string:
328831e0435a3137f6309807a88da234 encrypted with the key
2b28ab097eaef7cf15d2154f16a6883c results in the encrypted hexadecimal string
3902dc1925dc116a8409850b1dfb9732 and I get the same result.
Encrypting given test vectors however does not work with my algorithm and neither does encrypting the examples given in the animation with an AES encryption tool (which encrypted the test vectors correctly) work. Is there anything wrong with that flash animation or am I missing something obvious?