There should be 50px between top of B and top of A, OK in: Moz, Saf, IE5/Mac.
There are 50px between top of B and bottom of A (wrong) in: IE/Win, Op8-.
There is no space between top of B and bottom of A (?) in: Op9
There should be no space between B and A, OK in: Moz, Saf, Op9, IE5/Mac.
There are 50px between top of B and bottom of A (wrong) in: IE/Win, Op8-.
Like first case, but with an extra (blue, border-less) wrapper: follies! See negative clearance
There should be 50px between top of B and top of A, OK in: Moz, Saf, IE5/Mac.
There are 60px between top of B and bottom of A (wrong) in: IE/Win, Op8-.
There are 10px between top of B and bottom of A (?) in: Op9-.