The problem right there is in the definition of “liberal”. A cautious, forward-thinking designer-developer would interpret it as “allow for unknowns”. Whereas

The problem right there is in the definition of “liberal”. A cautious, forward-thinking designer-developer would interpret it as “allow for unknowns”. Whereas sloppy-ass cowboys think it means “accept any old invalid crap” and pass their garbage accordingly. One of these philosophies gave us HTTP; the other HTML. And no prizes for knowing which one is an utter horror to consume (an arrangement, incidentally, that works swimmingly well for its entrenched vendors and absolutely no-one else).