See documentation for the HTML 4.0 (XHTML) table model or OASIS (CALS) Exchange table model (XML version), dependent upon element involved.
The align attribute is used for aligning values in table cells on a particular character within each cell, frequently the decimal point. Alignment on a particular character requires that three attributes be set in the document:
|center||Center the cell contents|
|char||Align on the character identified with the char attribute|
|justify||Full justify cell contents (right and left justification)|
|left||Left justify cell contents|
|right||Right justify cell contents|
|Restriction: This attribute may be specified if the element is used.|