How to Disarm an Inaccessible Data Table (6th October 2007)
(In response to Better Connected, Better Results: Table Headers by RNIB. My message was always greeted with a 500 Internal Server Error.)
One idea is to treat <td><b> as though it means <th>. There are lots of other ideas. The Heuristic Tests for Data Tables (August 2007) and Heuristic Tests for Data Tables (September 2007) are where many of them are being discussed, prototyped and tested out. It's ongoing as part of HTML5's research and development.
We don't want to introduce an algorithm if it will fail most of the time, of course! My research is to see what authors are doing and whether hints like <td><b> are reliable enough for HTML5 to specify an algorithm which UAs would be expected to implement.
So far, it looks promising. But it’s too early to say for certain. Even when <th> is used, it sometimes needs more intelligence from the UA than to just go up from the current data cell and then go left from the current data cell. That's another aspect we are working on.
While I'm here, do you find that treating the first row as column headers and the first column as row headers works a lot of the time? If it does, that might help figure out tables which don't even use <td><b>.