• Examples
• Longer Descriptions
• Imagemaps

I have already done this to the headers on the HEASARC and EUD. If you have images on your pages, please take the time to add some brief descriptive text to your images.

EXAMPLES

<img alt="image" src="image.gif">
This isn't very useful since it doesn't give a blind person equal access to the information imparted by the image. Better would be:
<img alt="artist concept of the Chandra satellite in space" src="image.gif">

<img alt="*" src="/Images/gold_ball.gif">
Use of the asterisk alt tag is appropriate for bulleted lists that use images instead of <LI>. Be careful: if you use different color bullets to denote different things, make the alt tag different as well.

<img alt="" width=1 height=1 src="/Images/pixel.gif">
This is often used as a spacer. The blank alt tag is understood as such.

LONGER DESCRIPTIONS

If you feel the desire to describe a graph or chart in great detail, you should use a longdesc tag (note that there's *also* an alt tag):

<img alt="chart showing HEASARC Web access versus time" longdesc="chart_longdesc.html" src="chart.gif">

where chart_longdesc.html is an HTML file with plain text describing in detail what the chart looks like (x and y axes, shape of the curve, etc.) I've recently learned that this is not well supported and that a link (denoted with the letter "D") near the image that links to the longdesc.html will help many who use older assistive software.

IMAGEMAPS

If you have an image map with <area shape=...> tags, put an alt tag there defining where the link goes.
E.g. <area alt="HEASARC Home Page" shape="rect" coords...>.

Checking for Compliance

More 508 requirements

The web browsers for the blind also read pages in order. If you're sighted, you can determine with a glance that the navigation bars on this page are at the top and left, and you can very quickly determine where the real content lives. Screen readers don't have that ability. They will read this page in order of table cells: left to right and top to bottom. Blind users will hear every link (NASA logo, the seven across the top and the many down the left side) before any content is read. To alleviate this painful process, I have added an invisible link (you can find it at the top of the page a few dozen pixels above the NASA logo) which takes the user to the page content. If you're using the standard headers, this is taken care of for you. If you're developing new sites, keep this in mind and allow your visually-impaired users to skip the navigation and go straight to the content.

Try not to convey information solely by color-coding. You can now check what your pages look like to the color-blind.