VI. How To?
6.2. Accessibility Implementation Approach
6.2.1. Graceful Degradation
Graceful Degradation is the oldest approach; it is a fault-tolerant system. “The premise for graceful degradation is to first build for the latest and greatest, then add handlers for less capable devices. In other words, focus on the majority before catering to those outside the mainstream” (Olsson, 2007, p1).
For example the use of the alt="" attribute of the img tag is a graceful degradation; indeed, if the client is not able to display images, the content of the alt="" attribute will be displayed instead; it is not as pretty as the image would be, but it should carry the same information.
Another and more used example is the one of JavaScript codes. Any JavaScript code should come with a noscript tag offering an HTML only alternative in case JavaScript cannot be executed by the client. The presence of a noscript tag will also benefits to robots and thus to the website referencing. However, Timmy Olsson notes that with some particular network configuration, the noscript degradation is inefficient: “I may use a browser that supports JavaScript and has it enabled, but there could be a company firewall that strips incoming JavaScript for security reasons. In this case the noscript element will not be rendered (because my browser supports scripting) but the JavaScript code that should create the menu won’t be applied either, because it gets stuck behind the firewall” (Olsson, 2007, p1).
However, always in the case of JavaScript and the use of the noscript tag, some unscrupulous developers have been using code such as:
<script type="text/javascript" src="/menu.js"></script>
<noscript>
<p>Please upgrade to a browser that supports JavaScript.</p></noscript>
This is an improper use of the noscript tag. “We, as web designers or developers, have no right to tell our visitors which browser they ‘should’ use; nor do we have the right to tell anyone to 'enable JavaScript.' We don’t know why this visitor uses Lynx or why that visitor has disabled client-side scripting. They may not even have the option of ‘upgrading’ or ‘enabling JavaScript’ because of bandwidth, hardware or budget constraints; IT department policy; or because they are not even using their own computer” (Olsson, 2007, p2).