Animated elements and multimedia
Animation
When animating content care should be taken with timing to ensure it allows adequate time for the content to be read between transitions by all users (some users will take longer than others). A good rule of thumb is double the time it takes to read the content yourself. Transitions should be chosen so as not to flash between content, should any flashing content be necessary the user must be warned prior to it being shown. The user must have the ability to pause, stop or hide any moving, blinking, scrolling or refreshing content that lasts longer than three seconds. Do not use bright or flashing colours and moving or blinking text must be avoided.
Animated content that the user can not control must stop looping after five seconds or a maximum of three loops. Flashing content should also be limited to a maximum of three times a second. Epileptics may also have problems if there is more than one animated element used on a single page.
Descriptive text, such as alt text, must convey the same information as contained within the animated element.
Time limits
Try to avoid imposing time limits on processes. However where they are required always warn the user and provide them with a means to either disable or extend a time limit. Never redirect users automatically after a time delay as the unexpected change of context may interrupt the user.
If an authentication session expires, the user must be able to re–authenticate and continue the activity without loosing any data from the current page.
Users should always be clearly informed when they have been logged out either deliberately or due to a timeout. They should also be provided with a link to be able to log back in.
Audio and video
All videos, recorded PowerPoint presentations or audio recordings must have a textual equivalent such as a transcript provided. Also supply any important information via captions where ever possible. The addition of audio description or sign language interpretation should be provided if possible.
Enable control over playback with pause, stop and volume buttons and place these controls in context with the content it is related to. The volume should be independent of the user’s computer.
Do not auto–play videos on page load. Users should have control of this functionality. This assist able bodied users through not causing frustration and ensures that assistive technology users don’t have their journey interrupted.
Audio content should not contain background sounds, have the ability to turn off any background sounds, or have background sounds at least 20 decibels lower than the foreground audio content, with the exception of occasional sound effect.
Do not create pages with nothing but an embedded video on. If you do this, people without Flash will see just an empty page. Provide information within the page on what the video is about.
Using YouTube videos
Posting videos on video sharing sites, such as YouTube can be a very effective way to communicate our ideas. However you must consider accessibility requirements when you do so. Supply closed caption files of any dialogue when you upload your video and provide a text transcript of the video. If you like, you can provide captions in multiple languages, to increase your audience reach.
PDFs
PDFs are not automatically accessible to users of assistive technologies, but there are ways to improve their accessibility. When saving documents to PDF always specify that they should be ‘tagged’. This is normally done in the conversion setting dialogue. For example, in Word you need to ensure that the ‘Enable Accessibility and Reflow with tagged Adobe PDF’ setting is ticked. If you have inaccessible PDFs on your website, offer to provide an accessible alternative upon request. This can be done within your accessibility statement.
Check that an appropriate document title has been added. This is set within the document properties, and can be done in Acrobat or in the source file. On all pages that link to PDFs, provide a link to download the free Adobe Acrobat Reader.
Always ensure that a PDF is not made up purely of images if it contains textual information.