[whatwg] Reserving "id" attribute values?

[Brett Zamir]

In order to comply with XML ID requirements in XML, and facilitate 
future transitions to XML, can HTML 5 explicitly encourage id attribute 
values to follow this pattern (e.g., disallowing numbers for the 
starting character)?

Also, there is this minor errata: 
http://www.whatwg.org/specs/web-apps/current-work/#refsCSS21 is broken 
(in section 3.2)

Brett