When a web page requires that an applet, plug-in or other application be present on the client system to interpret page content, the page must provide a link to a plug-in or applet that complies with 1194.21 (a)(1-11).
Applets and plug-ins must satisfy the Section 508 software standards. In particular, they must be completely usable without a mouse. As focus moves from object to object, assistive technology must be able to determine the role and default action of each focused object. Test your use of applets or plug-ins using only the keyboard.