[CSS21] Containing block of internal table boxes

Hi,

My reading of section 10.1 tells me that the containing block of 
internal table boxes (eg. table cells) is the nearest block container 
ancestor box. That is, the parent or an ancestor of the table. This is 
probably not what we want.

Although the behavior of percentages on internal table boxes is largely 
undefined in 2.1, in practice they seem to refer to the table rather 
than one of its ancestor. The containing block should be one of the 
table box or the table wrapper box.

-- 
Simon Sapin