Do you mean the first 12 games ever put on AG? Well, there's a number of reasons why those could've been removed: AG rethought their expectations for games and these didn't meet them, the developers asked for AG to take the games down, and they probably weren't accepted when they were submitted.
If you change the URLs you can find the first few games submitted to AG. For example, this is Shell Shock Lives number: http://armorgames.com/play/11433 Change the "11433" to any number below it and you'll either get a game or the homepage. Not getting a game means that game wasn't accepted.
