[CEUD-ICT] Empty table header cells in HTML

[Alan M. Dalton]

Hello all,

Are empty table header cells acceptable in HTML, from an accessibility
point of view?

I've seen a couple of HTML tables that have empty cells that are marked as
table header cells. In those tables, all of the cells in the top row are
correctly marked as table header cells, and all of the cells in the left
column were correctly marked as table header cells. The top, left cell was
marked as a table header, but was empty. That seems wrong to me, in terms
of semantics.

However, I can't find any official guidance that says not to use empty
table header cells. The HTML 4.01 Specification says that "Cells may be
empty (i.e., contain no data)" [1] but doesn't differentiate between header
cells and data cells for that point.

The WCAG 2.0 technique, "H51: Using table markup to present tabular
information," [2] does not refer to empty cells specifically. It does have
an example HTML table with empty cells, and all of those empty cells as
marked as table data cells, and not table header cells.

In a 2005 article called "Accessible Data Tables" [3], Roger Hudson said to
"Avoid Columns of Empty Table Cells", but doesn't refer to single blank
cells. All of the blank table cells in his examples are marked as table
data cells.

So, are empty table header cells acceptable in HTML? Should they be marked
up as table data cells instead? Does it make a practical difference to
someone using a screen reader, mobile phone browser, or other device?

I'd be interested to hear your opinions.

Regards,
Alan.

[1] http://www.w3.org/TR/html4/struct/tables.html#h-11.2.6
[2] http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/H51
[3] http://www.usability.com.au/resources/tables.cfm

_
Alan Dalton
Accessibility Development Advisor for EtA http://www.nda.ie/eta
Access Officer for NDA http://www.nda.ie

Address: National Disability Authority, 25 Clyde Road, Dublin 4.
E-mail: amdalton at nda.ie
Telephone: 01-6080 406

EtA recipients 2008: http://tinyurl.com/EtA2008
_


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