"Bollaert, Jodi" wrote:

> Can anyone tell me...is there any usability issue in using alt tags as a
> descriptor for a graphic?

The issue is not usability but accessibility, to people with
disabilities and technological limitations.  See the W3C
guidelines on this and other accessibility issues:
  http://www.w3.org/wai/

> (I realize these should not be used to explain
> icons, which should be intuitive on their own.)

Not so.  They are needed for people who cannot see the icons,
especially blind people.

One should put ALT tags on EVERY image.  The idea of having them
pop up when the user moves the pointer over them is a side benefit
but is not the main point and should never interfere with their
use for accessibility ("never," that is, unless you know for sure
that your user population will have to be able to see for reasons
other than being able to use your web site -- say, if they're
airline pilots or something).

> Do all browsers support
> alt tags?

Do you mean "do all browsers pop up the ALT text when the pointer
is over the image"?  The answer is no.  None of the Macintosh
browsers I've used do this.

But all browsers support them in that they will display the ALT
text if the images are turned off or not loaded for some reason.

> Is there any way for users to turn alt tags off? Specifically, if
> I have an image of a corporate logo that doesn't include the company name,
> e.g. the Mercedes-Benz logo, is it considered good usability to use an alt
> tag to include the company name, or should there be a graphic caption?

It is good accessibility to use an ALT tag no matter what.  (The
content will depend on the purpose and other things, but the need
for an ALT tag is not in doubt.)

Elizabeth

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Elizabeth Buie                     Computer Sciences Corporation
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