Re: Accessibility: ALT for blank images with " " or ""?

On Thu, 04 Mar 2004 00:16:58 +0000, Chris Dudley wrote:

> Murilo Pinto wrote:
> 
>> In Brazil, most recommend the use of "spaced" ALT for images completely
>> meaningless. As all over the world, the recommendation is quite
>> different, I'd like to check w/ you what's your tech opinion on this
>> one.
>> 
>> I think that "aural" browsers will read the spaced ALT as a pause, a
>> comma. The null ALT, on the other hand, will be simply ignored, as it
>> should be for images conveying no information at all. Am I right?
>> Furthermore, is there a standard on this issue, like a w3 guideline?
>> 
>> Thanks in advance,
>> Murilo
>> 
> All accessibility guidelines I have ever read all say to use "". This
> causes the aural browser to skip over the image entirely. If there is an
> alt tag other than "" it reads it out. If there isnt one at all then it
> reads out the image filename. I have tested that much in the aural
> browsers I have to test with at work. I can check what happens with " "
> tomorrow if you like?
> 
> If I dont post back then remind me cos ive got the memory of a sieve ;-)
> 
> miko

OK did a quick test in IBM Homepage Reader 3.0

The following all have the same behaviour:

<img src="foo.gif" />
<img src="foo.gif" alt="" />
<img src="foo.gif" alt=" " />

In that nothing is mentioned about the image whatsoever. Alt tags are only
involved if the alt tag actually contains content.

Note that Homepage Reader is a Screen Reader not an aural browser. True
aural browsers are incredibly rare - the majority of visually impaired
users just use screen readers which interpret the HTML rather than
following the aural stylesheets (which in most cases dont exist anyway).

I then checked the file in Bobby Professional 4.0.

Having no alt text at all causes an error. It says if you dont want to
provide descriptive text then alt="" should be used. This tells
non-graphical browsers they can ignore the image (text browsers sometimes
list image filenames if no alt text is present).

If you have multiple images next to each other without space seperating
them then there will be no gap between the alt text for each image either.
This can be fixed by including the space in the alt text itself to avoid
"run together" problems (e.g. alt=" wibble ").

For more information than you could possibly want on alt text see this url:
http://ppewww.ph.gla.ac.uk/%7Eflavell/alt/alt-text.html

So in summary - use alt="" (the reason being for text based browsers not
for accessibility). 
alt=" " will cause a space to be displayed in text
based browsers - this is rarely what you want or expect to happen and can
cause some very bizarre layouts to be produced.

Hope that helps,

miko