2.1.109 [CSS-Level2-2009] Section 17.5.1, Table layers and transparency


The specification states:

 A "missing cell" is a cell in the row/column grid that is not occupied by an 
 element or pseudo-element. Missing cells are rendered as if an anonymous table-cell 
 box occupied their position in the grid.

Quirks Mode and IE7 Mode (All Versions)

Missing cells that have content are treated as anonymous table-rows, not cells.