There should be 50px between top of B and top of A: Moz, IE5/Mac, Saf OK.
There are 50px between top of B and bottom of A (wrong) in: Op (<9), IE/Win.
There should be no space between B and A: Moz, IE5/Mac, Saf OK.
There are 50px between top of B and bottom of A (wrong) in: Op (<9), IE/Win.
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: Moz, IE5/Mac, Saf OK.
There are 60px between top of B and bottom of A (wrong) in: Op (<9), IE/Win.