Use W3C documentation for the XHTML1.1 table model. (http://www.w3.org/TR/xhtml-modularization/abstract_modules.html#s_tablemodule)
Horizontal offset from the alignment character specified by the @char attribute; the percent of the current column width to the left of the (left edge of the) alignment character.
Alignment on a particular character requires that three attributes be set in the document: