HTML5, I love the idea but I often find myself having issues with the ongoing saga of politics around it. Faruk Ateş recently wrote of The Battlefield of HTML5 (it's a good read if you haven't already) and made one suggestion that I completely support, Modularised HTML5.
As I read Faruk's arguments for modularisation I felt completely in agreement but I was also nagged by a sense of dejavu. Modularised HTML, hadn't we already been here before? XHTML1.1 was basically just a modularisation of XHTML1.0 Strict, which was a reformulation of HTML 4.01 Strict in XML. These specifications are the basis on which HTML5 is built, so who forgot to follow XHTML1.1's great advancement of modularisation? If you would like more information on the argument for the modularisation of HTML5 then read Faruk's article. Of course, I have an additional recommendation to make.
Versioning HTML Modules
A specification is a lot like a piece of software or an API, it changes over time. Pieces get altered, pieces get removed and new bits get added. Versioning allows you to snapshot a point in the specification's development life and assign an identifier to that specific snapshot. Currently HTML5 is one big moving target and both developing with it and implementing it are a pain. Modularisation coupled with Versioning would better allow everybody to explain exactly what they support without slowing down the development of the specification.