We have used the example of the front page for an imaginary newspaper, implemented in basic HTML, to show how the look of a display on a computer screen can change to accomodate the abilities of the system. Although this is a rather basic example it should illustrate the point that graceful degradation, if it is possible, will allow a user to experience a good subset of the total content of the site or application without feeling excluded. You need also to consider whether a web page remains accessible to someone with differing abilities to your own.
A classic example of ungraceful degradation (or it is disgraceful?) is a web site where a visitor without Flash or even without a frame-capable browser just gets a message saying something like Your browser is out of date: go and get a new one. It happens.
|Red book, yellow book - CD Formats
Despite the introduction of DVD and DVD-ROM, the original compact disc format (CD) is still in widespread use and will remain so for a few years yet. It is interesting to see how the various forms of CD - including the obselete and obselescent ones - derive from each other. As DVD standards settle down a similar picture is emerging there as well. However in the case of DVD it is the video disc that underpins the other formats rather than the audio disc.
All CD formats are related and their specifications are described in a series of documents called the coloured books. The first was the Red Book which specifies the basic compact disc and CD-Audio, CD-ROM is covered by the Yellow Book, CD-i by the Green Book ... and so on. This document shows the family tree of the coloured book and associated 'standards'.