Images and Media
For most of us it would be hard to understand the web without images, audio, video & new interactive media. However, much of that information needs to be conveyed in an alternate format.
- Images
- Audio
- Video
- Interactive Media
Images
This is the most basic level, but also the most important for theme developers. Images that add to the meaning of a site should have alt tags for them that provide the missing context. If an image (such as a spacer) adds no context then it should have a blank alt tag (alt=""). Under no condition should an image use the file name as an alt tag.
As usual, WebAim provides a comprehensive & authoritative description of how to use alt tags. The examples help to explain to content creators how to define alt tags for a number of contexts including functional and decorative images. For images that convey more information than can be contained within 125 characters, it is recommended to use the longdesc tag so that the screen-readers don't divide the text.
Audio
For audio clips lasting more than 3 seconds that auto-play when a page loads, add an accessible feature near the beginning of the page to either pause or stop the audio or control its volume independent of the user agent's native sound system.
Provide a textual transcript of audio content, either on the page or linked near the audio content. If the content is live, provide text stating this and describing the live content. After the fact, provide a full textual transcript of the audio.
If the audio is a media alternative for text, no further transcript is needed.
Video
For time-based (non-live) media, provide an alternative with equivalent information or an audio track presenting the equivalent information. Be sure to place the link to text or media alternatives right next to the corresponding video content, and clearly identify any media alternatives to text as alternatives.
Provide open (always visible) or closed captions on video content.
Interactive Media
TBA: in short, provide a long description that provides the context of the interactive media. See WebAim's article on Flash.