[css3-conditional] Supported vs. valid declaration.

Hi,

About sections §6.1 and §6.2, is there a difference between:

1. a declaration being 'invalid' (and thus being ignored by the parser 
to allow old-style fallbacks)
2. being 'not supported' (resolving to false in @supports)

?

I’m thinking in particular of 6.2’s comment on values that might be 
valid in a spec but the UA "do not have a usable level of support for".

I think that the two notions should be the same, and that 6.2’s comments 
should apply to both. CSS 2.1 was less clear on this subject, only I’m 
not sure that it’s within css3-conditional’s scope to affect the parser. 
Should this last part go into css3-syntax?

-- 
Simon Sapin