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Re: using 'hidden' for data table

for

From: Jukka K. Korpela
Date: Sep 15, 2004 2:07PM

On Wed, 15 Sep 2004, randyp wrote:

> Apologies for thread creep, but this topic so similar to the current:
>
> We have some web-based tables of numbers, wherein a healthy percentage of
> the
> cells' value is 0. To draw visual attention to the non-0 cells, some have
> suggested blanking out the 0's, so those cells are empty.

As a side note: this raises the problem that browsers may treat completely
empty cells differently in visual rendering, e.g. not drawing borders or
not using a background color that has been specified. Usually a space
counts as completely empty, no-break space ( ) doesn't.

> Is there an
> accessibility argument against doing this? It would seem so, as the concept
> of "blank meaning 0" may not be obvious via screen reading or other
> alternative types of access.

Indeed. It might not be evident in "normal" types of access either.
The user's first question might be "why have they left out some
information here?".

There are various practices of indicating different types of "emptyness"
in statistical tables, e.g. so that ".." means 'data not available',
"-" means an exact value of zero, and "0.0" means that the value is zero
when rounded to the precision used. Naturally such notations should
normally be explained e.g. in a legend on the right of the table (and
using floating in CSS you could arrange things so that the legend appears
before the table in HTML markup, hence gets read first by a speech browser
that directly reads the HTML source).

For some more notes on empty cells (mostly related to visual
presentation), see
http://www.cs.tut.fi/~jkorpela/html/emptycells.html

--
Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/