This step computes the defined margins, the border and paddings. Before margins and borders can be computed, this derives the block-context-width.
The block-context-width is a precomputed value and defaults to the total page width (or when there is no such width, a predefined value). The block-context-width is independent of the final size of the element.
Table-Cells establish their own context, if the width is known. (This adds the dependency, that the table structure must be validated before the static properties can be computed.) If the width is not known, the block-context-width will be undefined (zero) unless a new known context gets established.
@author Thomas Morgner