Graceful degradation

Sometimes you need to be aware of how your application will behave and look when it is used on a computer platform with fewer capabilities and features than the' optimum' for which you designed it. If the application still performs well and adapts to make good use of what is available to it then it is said to be degrading gracefully.

It might be that there are fewer colours possible with the display, or that there is no sound, or that the screen is smaller. Ideally the application should still work and seem to be complete, even though it may look and behave differently.

Perhaps the most interesting current examples of graceful degradation (or not) occur on the Web due to the behaviour of web browsers and the presence or absence of plug-ins. Since a mark-up language is used to describe the layout of a document, such as this one, it is likely that different browsers will display the page differently.

To show how exactly the same 'program' (in this case an HTML document) can look when all its features are implemented, and how it looks on a simpler browser, we have concocted the front page of a newspaper from an imaginary holiday resort. (These will open in a new window.)

Original Version

'Degraded' Version

The original version of the document shows the 'bells and whistles' whereas the 'Gracefully Degraded' version shows how it might look on a lesser-featured browser; without tables or in-line graphics (assuming there are still some of these about - believe me there are!). In theory, you can get the same information from both even if they look different. Of course this is a very simplistic example given that we could be using Java, JavaScript or Flash to achieve the desired visitor experience.

Accessibility to visitors with differing abilities will increasingly affect how web pages are built. At a simplistic level you should consider how the page will perform without images (but using ALT and LONGDESC tags to describe the images) and how a screen-reading browser might read the page aloud for someone who can't see it.