Part of the problem with the WHATWG HTML 5 specification is that it’s primarily written by browser makers. (Hixie, its editor, is the exception, as he currently works for Google, though in the past was employed by the Mozilla Foundation and Opera.)
This has steered the focus of the specification towards browser manufacturers — the specification includes such things as algorithms for parsing markup. To expect a typical document author to care about such details, let alone understand them is a triumph of optimism over sanity.
The aim of most browser makers is to increase their market share — to attract users, the browser must enable them to view any documents they could in their old browser, plus tempt the user with an array of new features and improvements. Naturally this leads to a situation where browsers are somewhat liberal in interpreting documents.
Whatsmore, it tends to mean that tolerences of malformed HTML in one browser proliferate.
Paving the Cow Paths
HTML5 embodies a principle called “paving the cow paths”.
The idea behind this analogy is that at some time ago, a lonely cow wandered haphazardly through a field. A day or so later, a man walking through the same field decided to follow the trodden down path instead of venturing into the long grass. Over time, many people following the same path wore it down into a dirt path where no grass would grow. This was eventually paved.
Nobody seems to have mentioned to WHATWG that this isn’t a good thing. You end up with a haphazard road rather than a straight, efficient route. You end up with and