Text equivalents are used to convey meaningful information about a non-textual object when it cannot be rendered and/or interpreted by a browser, assistive technology or perceived by the user. Besides providing text-based explanation, they can be used as an opportunity to reinforce the message being conveyed by the image. Text equivalents can be provided by using:
ALT attribute- to convey short description of an image. Some browsers display them as "tool-tips" when a mouse hovers over the image.
<img src ="trigfunc.circle.gif" alt="Circle showing trig functions" width="210" height="200">
LONGDESC attribute - to convey a richer description of an image when the short description is not sufficient to convey the full meaning. This is an HTML link to another web page, however, not all browsers support this attribute.
<img src ="trigfunc.circle.gif" alt="Circle showing trig functions" width="210" height="200" longdesc="trigfunc.html">
D-link or descriptive link - is also used to convey a richer description of an image. This is a separate link associated with the image and and is used as an alternative to <LONGDESC>
<a href="trigfunc.html" title="link to detailed description of image"> D</a>
TITLE attribute- is used to annotate most elements. They are displayed as "tool-tips" by graphical browsers and as text for non-graphical browsers.
<img src ="trigfunc.circle.gif" alt="Circle showing trig functions" title="Circle with a perpendicular triangle showing the sin and cosin of the right angle" >
Text Description of Object -this is the description of the richmedia object placed within the <object> element
An animated clock.
Descriptors of Video Content is required for visually impaired users. The descriptions of video can be provided on the page or as a link associated with the object. D-links can also be used for text descriptors.
Text Transcriptions is required for all audio content. The tanscript can be provided as a link associated with the audio object
Captions are syncronized transcripts of audio and video content.