Text browsers and screen readers cannot convey images to their users. To compensate, it is important to associate alternative text with all images, especially for active images, i.e., images which are links or buttons. The alternative text should be meaningful, like "home page" or "search" or "products." When images are not links, use alternative text carefully. A person having to listen to a page cannot ignore text the way a person viewing the page can ignore an image. If images are not important or if they are redundant, use alt="", telling the text browser to ignore the image.

The use of alternative text is not just for people who are blind; alternative text is also used by voice recognition software. Links which are images are not accessible to voice recognition software unless the author has provided alt text for the image. The user, navigating the Web with voice recognition software, can say "click home page" for the image whose alternative text is "home page" and be taken back to the homepage.

A page with no "ALT" tags leaves the vision impaired user guessing!

A short (10 to 15 word) description can provide navigation tips and a "comparable" web experience for the visually impaired or those surfing your site with graphics turned off. An example "alt="Link to next page"

Sometimes when using graphics to convey information, the short description provided by "alt tags" isn't adequate.

One alternative - the "long description" or longdesc tag linking to an HTML document

<img border="0" src="age.gif" alt="This chart shows prevalence of disabilities as they increase with age" longdesc="aging.htm">

Not all browsers support the long description-
A second alternative - the "D" or description link - the "D" link is a link to an HTML or text document conveying the same information. 

<img border="0" src="age.gif" alt="This chart shows prevalence of disabilities as they increase with age" longdesc="aging.htm">[<a href="aging.htm">D</font></a>]

When graphics are used in lists

• National Weather Service
• National Environmental Satellite, Data, and Information Service
• National Ocean Service
• National Marine Fisheries Service
• Office of Oceanic and Atmospheric Research
• Office of Marine and Aviation Operations

With no "Alt" tag, screen readers will repeat "image National Weather Service", "image National Environmental Satellite, Data, and Information Service", "image National Ocean Service", "image National Marine Fisheries Service", etc.

If using an "Alt" tag of "blue dot", the user gets "blue dotNational Weather Service", "blue dotNational Environmental Satellite, Data, and Information Service", "blue dotNational Ocean Service", "blue dot National Marine Fisheries Service", etc.

Instead, use a short word (i.g."item" for the first item in the list) or an asterisk "*" or tilde"~". (many users of speech readers do not have punctuation"read" to them). If it is a longer list, use a space between two double quotes " " to prevent the user from hearing "asterisk... " repeated over and over.