[CSS21] Height of block whose child has 0 height and/or clearance

This is related to the "Floating - who's right?" thread. The 10.6.3 text  
seems to have multiple problems.

1. Talks about "child box"es even though the formatting structure is  
basically undefined (if interpreted as "child element's box" it's even  
more broken)

2. In the "block-level children" case, defines height as the distance  
between edges of boxes that do not have margins collapsed through it -  
what if there is no such box?

3. What if the "topmost block-level child box" has clearance? This case  
doesn't seem to be considered.

4. The case of no content at all probably requires special mention too

-- 
Øyvind Stenhaug
Core Norway, Opera Software ASA