Reported by Anton Prowse

(A)

8.3.1 (Collapsing margins) says in a note listing various practical
implications of the margin collapsing rules:

  # If the top and bottom margins of an element with clearance are
  # adjoining, its margins collapse with the adjoining margins of
  # following siblings but that resulting margin does not collapse
  # with the bottom margin of the parent block.

However, the concept of adjointness is intransitive and so is common (as per previous versions of the spec) that the margins of the clearing element need to collapse despite not being mutually adjoining.  Hence the sentence needs reformulating in terms of collapsing:

s/are adjoining/collapse/

and maybe also
s/its margins/then they also/

See: http://lists.w3.org/Archives/Public/www-style/2010Aug/0364.html


(B)

8.3.1 says:

  # If the top and bottom margins of a box are adjoining, then it is
  # possible for margins to collapse through it. In this case, the
  # position of the element depends on its relationship with the other
  # elements whose margins are being collapsed.

s/are adjoining/collapse/

since we need to define the position of a collapsed-through element even 
when its top and bottom margins are not adjoining, which would be when 
it has a (necessarily self-collapsing) child.

And, for readability,
s/for margins/for other margins/

See: http://lists.w3.org/Archives/Public/www-style/2010Aug/0364.html
     http://lists.w3.org/Archives/Public/www-style/2010Sep/0698.html

Anyhow, it's not clear whether "In this case" refers to the margins being adjoinging or to other margins collapsing through it.  The whole sentence could be changed to:

  | If the top and bottom margins of a box collapse, the position of the
  | element is determined as follows.

See: http://lists.w3.org/Archives/Public/www-style/2010Aug/0364.html