According to the CSS2 Table Model:
"Table cells may be relatively and absolutely positioned, but this is not recommended: positioning and floating remove a box from the flow, affecting table alignment."
position:relative should apply to
display:table-cell, and child elements should be able to be positioned relative to that coordinate space.
Mozilla (1.7) ignores the position:relative property; Safari (1.2) changes its behavior, but not in a correct way; IEWin seems not to properly support
bottom:0 inside the table cells.
Conclusion: Yet another reason not to use tables for layout! :p (Seriously, this does have non-evil uses, as seen here.)