Alt

Alt tags, for alternative content, are contained in the "Img" element and provide a description for screen readers and text browsers to read instead of source codes for images. They also provide alternative content for mobile devices and users with slow connections or images turned off. A-Prompt recommends that Alt text be 10 words or less. Alt tags are crucial to providing accessible content, since it is rare that the location of a file a will be useful description.

For example, without the Alt tag, a screen reader would describe the image link below as "/Images/Over65E.jpg." With the Alt tag it would read "Percent of U S Population over 65 from 1900 to 2050."

Code Example:

<p>
<img src="../Images/Over65E.jpg"
width="350" height="231"
alt="Percent of U S population over 65 from 1900 to 2050">
</img>
</p>

Additional information, for example about the content of the image, can be provided two ways, through a a D-link, literally a link that is shown as "D", for description, or a link using the Long desc tag.

"D" Link Example

<p> 
<img src="../Images/Over65E.jpg"
width="350" height="231"
alt="Percent of U.S. population over 65 from 1900 to 2050">
</img>
 
<a href="Over65Description.html"
title="Detailed description of increase in people over 65">D</a>
</p>

Long Desc Example

<p>
<img src="../Images/Over65E.jpg"
width="350" height="231"
alt="Percent of U.S. population over 65 from 1900 to 2050"
longdesc="Over65Description.html"
title="Detailed description of increase in people over 65">
</img>
</p>

Browsers

Internet Explorer displays Alt text when a cursor passes over an image. Netscape Navigator does not. Neither displays Alt text when tabbing through a document.

Adaptive Technology

Both Home Page Reader and JAWS read Alt text instead of source code when reading through a document. They ignore graphics when tabbing through a document.