from https://lists.w3.org/Archives/Public/www-style/2013Jun/0683.html
issue opened to be sure the resolutions were implemented
Conditional Rules / Syntax
RESOLVED: Whenever error-recovery closes open blocks, urls, strings,
functions, brackets, etc., it implies the minimal tokens to
close those constructs.
RESOLVED: [EOF] turns into U+FFFD except when inside a string, in which
case it just gets dropped.
RESOLVED: Clarify that badstring and baduri make @supports rules invalid
RESOLVED: !important allowed in @supports
RESOLVED: Publish CR with updates for CSS3 Conditional Rules