Web sites are increasingly using more advanced and complex user interface controls, such as tree controls for Web site navigation like the example in Figure 1. To provide an accessible user experience to people with disabilities, assistive technologies need to be able to interact with these controls. However, the information that the assistive technologies need is not available with most current Web technologies.
Another example of an accessibility barrier is drag-and-drop functionality that is not available to users who use a keyboard only and cannot use a mouse. Even relatively simple Web sites can be difficult if they require an extensive amount of keystrokes to navigate with only a keyboard.
Many Web applications developed with Ajax (also known as AJAX), DHTML, and other technologies pose additional accessibility challenges. For example, if the content of a Web page changes in response to user actions or time- or event-based updates, that new content may not be available to some people, such as people who are blind or people with cognitive disabilities who use a screen reader.
WAI-ARIA addresses these accessibility challenges by defining how information about this functionality can be provided to assistive technology. With WAI-ARIA, an advanced Web application can be made accessible and usable to people with disabilities.
W3C official documentation: https://www.w3.org/TR/wai-aria-1.1/#aria-rowcount
ARIA Authoring Practices: https://www.w3.org/TR/wai-aria-practices-1.1/