@KrzysiekJ I've been bugged by this for as long as I can remember. Standards are agreed upon, then discarded for the sake of convenience. Major browser being less strict is considered a "competitive advantage", as from the nontechnical user's viewpoint, they are the ones that "work" with those sites unlike others.
But there seems to be no adequate way to fight this behavior. Standards can't really be enforced by anyone other than browser creators.
@KrzysiekJ what is even more strange to me is why these vendors won't push for a liberalization of the standard in such cases? This would still leave them with the competitive advantage of being the ones who have implemented them "properly" first, while pushing for more consistency on the web.
I'm not even touching on the subject that this behavior reinforces sloppiness, lack of care for coding standards and general ignorance.