empty table cell size

If a table cell is empty and empty-cells:hide is set and there are other 
cells with content that will hinder the row to be hidden, what width 
will this cell occupy if both border and padding are > 0?
Should these cells treated like they have visibility: hidden specified? 
If yes, couldn't the spec be made more precise on this, as some browsers 
differ already on the size handling.

Bernd