The letters IHS were the first three letters of the Greek name of Jesus IHSOYS, which stood for Yahweh.
Just a nitpick (and I know you're quoting another site): The Greek name of Jesus is IHSOYS in Greek letters, or Iesous transliterated into English letters. It doesn't stand for Yahweh, God's name used in the Old Testament. It just says Jesus.
Awesome comment though.