In case someone wants to prosecute me of a crime, can I be excused from the punishment because of the Q&A in avvo.com?

No judge or prosecutor would accept that explanation.

No, ignorance of the law is not a justification for acting unlawfully.

Not at all! In fact they will probably just roll their eyes at you.

No. I have no idea why you would think that is a good idea. Even if you had a fully retained lawyer, that excuse would not help you in court. I am curious, though, as to what a lawyer supposedly told you to do that turned out to be illegal. I'm betting that you misunderstood or did not properly follow his or her suggestion.