"WAI-ARIA, the Accessible Rich Internet Applications Suite, defines a way to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with Ajax, HTML, JavaScript, and related technologies."

Apart from the general benefits of this - when dealing with government organisations, including local councils, they will most likely insist on compliance to this standard.

In using the ibCom onDemand application framework in combination with jQuery, a lot of the work is done for you - via inherent compliance, ARIA jQuery plugins and dyanmic control over the stylesheets.

http://www.w3.org/WAI/intro/aria.php