axis Attributeaxis AttributeThe axis attribute is intended to help assistive technologies
categorise the content of table cells, making it easier to
interpret the table. However, support for axis is almost
non-existent so I won't go into detail here.
There's nothing to stop you using the axis attribute, of course:
future user agents may well start supporting it. However, your tables will
always be more accessible if they're simple enough that they don't
need axis in the first place.
For reference, you can find the (HTML) W3C documentation at *HTML 4.01 - Categorising cells.