Assistive technology users should be able to detect when important changes occur on a web page, With the use of a status message, information can be provided to the user without changing focus or unnecessarily interrupting their work.
For a number of reasons including data persistence, performance and security, it is sometimes beneficial to terminate idle user sessions. It's important to warn people a session is about to expire and give them the option to continue.
Providing form feedback accessibly helps users submit data more accurately and reduces the chance for error.
Modal dialogs can enhance usability by focusing attention on a specific message that requires a user action to continue.
An accessible modal dialog is one where keyboard focus is managed properly, and the correct information is exposed to screen readers.