TIP 39

Don't think everyone has got the same software has you

Design for Platform Independence

While most web browsers can easily read HTML and display it to the user, several private companies have developed proprietary file formats for transmitting and displaying special content, such as multimedia or very precisely defined documents. Because these file formats are proprietary, they cannot ordinarily be displayed by web browsers. To make it possible for these files to be viewed by web browsers, add-on programs or "plug-ins" can be downloaded and installed on the user's computer that will make it possible for their web browsers to display or play the content of the files.

This provision does not forbid the use of plug-ins and many of the existing products support these features. If a browser does not support these features, however, than some other method of working with the web page must be provided. This provision requires that web pages which provide content such as Real Audio or PDF files, also provide a link to a plug-in that will meet the software provisions.

This provision places a responsibility on the web page author to know that a compliant application exists, before requiring a plug-in. As assistive technologies advance, it is anticipated that the occasions when the use of scripts and plug-ins are not supported will diminish significantly.

Techniques

• Create a link for the user to obtain a plug-in if your using, for example, Quicktime movies.

UK Government recommendations:

'Developers should ensure that web pages are not dependent on a certain resolution, colour depth or font size.'

Guidelines for UK Government websites
Illustrated handbook for Web management teams

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