niniendowarrior: I am not as smart as you.
No worries. So, once again, code formats.
GOG gift keys are in the format of "XXXX-XXXX-XXXX-XXXX", though "XXXXXXXXXXXXXXXX" (16 characters) will also work.
GOG Bonus codes are in the format of "XXXXXXXX" (8 characters) and have an expiration date.
Steam keys are in the format of "AAAAA-BBBBB-CCCCC", "AAAAA-BBBBB-CCCCC-DDDDD-EEEEE" or "237ABCDGHJLPRST 23" (going from the Product Activation of steam).
Desura keys also come in (at least) two versions, the 25 alphanumeric digits one, and the 14 digit one which is usually from IndieRoyale, and is also the IndieRoyale's page (which contains the DRM-Free links and you steam codes).
Not sure if I missed any other key format, but I'm sure someone will correct me if that is the case :)