[css3-cascade] Unclear what 'default' does

The css3-cascade WD of 2013-01-03 says, in 4.3.3:

   # If the cascaded value is the ‘default’ keyword, then the origin
   # level to which it belongs is discarded from the cascade, resulting
   # in a new cascaded value.

I honestly don't understand what it means to "discard" an origin level 
from the cascade!  Please can somebody explain (by way of example), as 
well as clarify the spec (by way of new prose). :-)

   # For this purpose, all author-originating styles (author and
   # override, both normal and important) are treated as belonging to
   # the same origin level.

I'm confused by what, precisely, an origin is.  I think it's because the 
"Origin" subsection of 4.2, and 4.2.1, contradict each other.  Is an 
origin a function of !important, or not?

I assume that if 'default' is used in a /user/-originating style, the 
origin to be "discarded" is a function of !important, and so 'default' 
is less powerful in the User context than in the Author context.  Is 
that correct?

Cheers,
Anton Prowse
http://dev.moonhenge.net

Received on Monday, 14 January 2013 20:56:23 UTC