##Implementation issues
###How do we expose declaration blocks from at rules?
CSSMediaRule instances could be exposed as flags through the content property of a pseudo element (applied to html/body?), and consumed through getComputedStyle. What about other forms?
###How do we deal with merging property shorthands? { background: red }, { background: url('...') yellow }
The 'style' attribute can only contain property declarations
I agree that you can replicate user-interaction pseudo classes (
:hover,:activeand:focus) relatively easily. However, for every other category, we'd end up introducing a neutral element purely for the purpose of styling :(hovershould be considered a mandatory accessibility requirement in most projects, so it needs to be supported.