I guess that it was my fault. Please see my update above. I understand perfectly that we all cherish our program and don't want others to modify it, as if there was something wrong with it.

I really don't want you to take it in the wrong way, and I am sorry if I made you felt bad, although it was not my intention. My intention was definitely not what you thought it was, and I was not commenting your code. I was merely try to prove that it was a bug, but from a HTML specification point of view.

Put in this way, had the coverted HTML with DOCTYPE at its end also passed the validation, as did the original one, I would have probably said that it was not a bug.