An attempt to find what is considered to be illegal internet content can be partly described by the Computer Crime wiki page.
I would summarize illegal content to be any content, images, code, or software that executes or promotes:
Yes, Showbox is considered illegal in the United States as it provides access to copyrighted content without proper authorization.
Yes, internet gambling is illegal in some states but allowed in others. Recently, betting on internet poker has become illegal throughout all states.
Downloading uTorrent the program is legal in the United States. However, if one downloads pirated content using uTorrent, then it is considered an illegal download.
No adultery is not illegal in Louisiana. Adultery is not illegal in most states but it is considered immoral.
Yes. It is illegal to make death threats in any form in all states.
Adultery is considered a criminal offense in the states of Idaho, Michigan, Oklahoma, and Wisconsin.
Yes, in most states its considered to be obscene
Disney refuses to release this film in the United States because it is considered racist by today's standards. However, it has been released in Europe. It is not illegal if you have purchased one of those copies. But if you downloaded it off the internet from a non-Disney website, that would be illegal.
Yes, it is illegal to destroy money in the United States as it is considered a violation of federal law.
All states have a zero tolerance for underage drinking. If the blood content is .02 or higher it is illegal.
Not in the United States, unless you pladiarize copyrighted content.
Yes, blackmail is illegal in all states. It is considered a criminal offense to threaten someone in order to obtain something of value from them.