DEMOS Project - Accessibility Guide: DHTML/Multimedia

Alternatives to dynamic and multimedia content

If you are offering audio or visual content such as sound clips, Quicktime movies, photos, animations, diagrams etc, make sure to offer alternative formats. For example, transcripts of audio files, captions for video or detailed descriptions of the content of photographs. (See the chapter on Graphics and Colour.)

If you are using Dynamic HTML (DHTML), techniques such as CSS and JavaScript, or if you ar using technologies like Flash, keep in mind that these might not be supported in older browsers, might require special plug-ins or are often turned off for a number of reasons, from load-time to security.

Content should remain usable and readable even when these technologies are not supported or turned off. If advanced techniques are used, it might be necessary to provide an alternative. Do not rely on them alone to convey information and provide functionality.

The WAI Guidelines include instructions on:

Text-only versions

Imagine the following scenario:

A blind person visits a news site but finds that his screen reader has difficulties with the complex layout. He tabs through the links to find a link to a text-only version but gives up after a while without discovering that the link he was looking for is at the bottom of the page.

Many web designers provide text-only versions of their webpages. If you use this option make sure that a link to this text-only version is included near the top of every page. All too often these links are placed at he bottom of the page, making it unlikely that the user will ever find out that an accessible version exists.

These text-only alternatives are often used for graphics or script heavy sites. Flash sites, for examples, which are often slow to download and require special plug-ins for the browser, should offer an alternative way of accessing the information contained within the site.

It is important to keep both versions of a website synchronized. When one version of the site is updated, the alternative version needs to be updated too.

Print versions

Text-only versions are also used to offer a printable version of a page, without colour, graphics, advertising, navigation. Because this page will then exist outside the context of the website it is important to include certain information, e.g. the URL of the original version.

Read this article for more information:

A better printable page, by Joe Clark.

Flash accessibility

In April 2002 Macromedia released the Flash MX authoring environment and the new Flash 6 player to address some of the accessibility problems presented by Flash content, e.g. compatibility with screen readers.

An analysis can be found here:

A List Apart: Flash-MX: Clarifying the Concept, by Joe Clark.

A List Apart: Flash-MX: Moving Toward Accessible Rich Media, by Andrew Kirkpatrick.

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