Notes:

TD offsetLeft: 
    mozilla includes the tables border-width when the TD contains block-level children. BUG.
    Except TD is inside a TR that has position: relative AND the TD contains block-level children.

TD offsetLeft:
    Safari, offsetParent is TABLE; does not include TABLE clientWidth (must add clientWidth)
    Opera offsetParent is TABLE's offsetParent; offsetLeft is correct
    IE, Moz: same as Opera

#spanPar offsetParent
    Only IE gets this one right. It's the documentElement, and that is because BODY has position: static.

XXX IE - Any TR position: relative affects TBODY in IE. IE moves row (or cell) with top: 12px; left: 12px;

The table API is complicated and doesn't have any formal definition. It needs one.