All content images on this site are provided with descriptive ALT attributes. Where images contain important information, such as graphs and charts, alternative information is provided in the form of inline descriptions of tabular data.


Our site uses CSS (cascading style sheets) for visual and design layout this enables users to customise the appearance of the site to their preferences. Users without CSS will be able to browse a hierarchical list of contents.


We use Adobe Flash Player 7.0 or newer only for video purposes. We recommend using the most recent version of Adobe Flash Player, which is available from Adobe.