[gsnedders]

> HTML5 doesn't refuse to accept anything that HTML 4 accepted.

It does. It doesn't accept NET syntax, i.e., `p/This is contents of a p elements/`. (No browser ever supported this, but because HTML 4 is defined to be an SGML application and it's DTD allows NET syntax to be used, it is theoretically conforming HTML 4.)

[eyelidlessness]

Ah good point, thanks for the correction.

[gsnedders]

(There's also another load of SGML bits of syntax that browsers have never supported which HTML5 doesn't support. Indeed, HTML 4 has a whole section of such things: http://www.w3.org/TR/html4/appendix/notes.html#h-B.3.3)