Originally Posted by meme
But if anyone who knows the spec and the site well can confirm it really should be CSS 2 let me know.
ePub uses its own subset of CSS, it's not 2 nor 2.1 nor 3, according to the spec:
This specification defines a style language based on CSS 2. (Note that the CSS 2.1 specification is currently still at "Working Draft" status.)
A conforming Reading System must
render all OPS CSS 2.0 required subset properties
. A Reading System may
support CSS properties beyond the OPS CSS 2.0 required subset, however, any unsupported properties must
be gracefully degraded per the CSS 2.0 specification.
Regarding the syntax, I don't think there's any difference between standard CSS and ePub-flavoured one, but as for the supported properties and values there are some important changes/limitations.