Creating a richer experience in the browser using Ajax has often meant excluding, unintentionally but significantly, large portions of the browing population: users with disabilities relying on assisted browsing technologies like screenreaders.

The W3C's Web Accessibility Initiaitve, which has long been the center of discussion for standards and technologies to make the web more accessible, has created a set of activities under the broad title WAI-ARIA (Web Accessibility Initiative Accessibility in Rich Internet Applications).

The goal of WAI-ARIA is to enable rich internet applications to work with assistive technologies:

WAI-ARIA addresses these accessibility challenges by defining how information about these features can be provided to assistive technology. More specifically, ARIA provides a framework for adding attributes to identify features for user interaction, how they relate to each other, and their current state. With ARIA, an advanced Web application can be made accessible and usable to people with disabilities.

For example, the Dojo Toolkit, an open source framework for creating rich internet applications, has been working to ensure that Dojo widgets are fully accessible using the techniques recommended by ARIA. 

The more that frameworks and toolkits take into account accessibility issues, the more likely it becomes that developers will build accessible applicaitions.