Sometimes it is easier to explain something by using an animation. For example, have you ever tried teaching someone to tie a knot using words (text) only? A video is often full of extraneous information, so a simple animation is best, so long as it is presented in an accesible format !
Animations written using Flash can be really useful in explaining concepts or demonstrating ideas. For many users Flash animations really bring websites to life. However these animations need to be delivered properly.
The first thing is to provide a method to avoid the animation for users who might have problems accessing them. This might be a "skip animation" link BEFORE the animation , or a warning that a particular link will take the user to a section of the website that uses Flash animations. It is important that any warning, such as a skip link (to skip the animation) is clear to visual users as well as to blind users. Large Flash animation files can completely fill the buffer of assistive software and result in freezing up the users computer.
If you have a complete website written in Flash then you need to provide a link to an alternative website that does not use Flash. Make sure that this alternative site offers the same service or information as the Flash site.
When using Flash animations please use the accessibility options and tips available from Macromedia. These tips provide ways for the user to control the animation with the keyboard as well as with a mouse. If you include any Adobe Flash or Adobe PDF files on your website you should visit the Adobe Accessibility Resource Centre (link available at the end of this lesson).
Once you have created an animation (using any available accessibility options) you should embed the animation in such a way that if the user cannot see the Flash animation they get a text alternative. In the following example we have used the <object> element to include a flash movie on the page. Using a similar approach to that used for the <iframe> element we have included a link to another page where a desription of the animation can be read in text form.
Sample of code follows
<object width="550" height="400">
<param name="movie" value="somefilename.swf">
<p>some text or a link to another page</p>
In the example above most users who have Flash would see the animation object "filename.swf". Users who do not have Flash get the alternative text or link dispalyed on their screen. Because a browser works down through the <object> attributes until it finds one that it understands, the last attribute should always be a text alternative or link to a standard HTML page.
If you are using animations, such as Flash, that require the user to install an additional "plugin" for their browser you should provide a link to where the user can obtain the relevant application. Please do not automatically re-direct non-flash users to the download service as this changes the focus of the page without warning and causes serious problems for blind users. You should always warn a user before you change a window, and always give the user the option to reject the change.
Horizontal scrolling text (sometimes called "marquees") are not just annoying, they can casue real problems for disabled users. The speed of the scroll can be too fast or too slow for the user, the movement of the text can make it impossible for people with dyslexia to read. If the speed matches a screen readers default reading speed it can create an infinite repeating loop on the first letter making progress impossible. For these reasons you should never use scrolling text unless you provide an alternative page that does not use scrolling AND warn users before they follow any link to a page that has scrolling text.
Flashing images and movement on the page
Anything that automatically moves about the page, flickers, or flashes can cause distraction to the user. For this reason such elements are best avoided. However if you do include them you MUST provide a clear method for the user to stop the movement or animation.
Under certain conditions flashing images can cause epeleptic fits. To avoid this any flashing or flickering image must not cause the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz.
Not everyone can absorb content at the same speed. When including animations (or other multimedia) it is important that you also include some mechanism so that the user can pause the animation whilst they have a think, (or stop to chat to someone). Most media players such as Windows Media, QuickTime and RealPlayer all provide control buttons as standard but animations such as Flash need you to add controls to the animation yourself. The techniques for including controls in multimedia are not covered in this set of lessons, you will need to refer to the manual for your authoring programme.