Why is the HTML version in Windows Mobile 6.5 in 4.01 and Not 5?

One of the questions asked at the Sydney Windows Mobile Debug Day was what version of HTML does Windows Mobile 6.5 Internet Explorer Mobile, and subsequently Widgets, support? The answer is that IE Mobile 6 supports HTML v4.01 (as well as javascript 5.7). This received a bit of debate since the Palm Pre offers support for HTML 5 and as such wouldn’t Microsoft want to future proof their platform.

I think one thing to remember is that most OEMs who build and sell Windows Mobile phones do not offer regular or frequent updates to the ROMs, and unlike some platforms, Microsoft is unable to push out updates when they make changes to the core platform.  Why is this relevant? Well, if you are across the HTML standards you will know that HTML 4.01 is “a stable document and may be used as reference material or cited as a normative reference from another document” (from the W3C HTML 4.01 Specification), where as the HTML 5 “specification is not stable” (from the W3C HTML 5 Specification) and they further state:

Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the aforementioned mailing lists and take part in the discussions.

Whilst I’m sure that Microsoft has representation on the appropriate committees/lists, I would suggest that it is a little presumptuous to implement HTML 5 on a device that is no easily updatable. I guess we can only hope that the HTML 5 specification is locked down in time for the next version of Windows Mobile.