Error "500 Servlet jspservlet: ..."

When the user enters the AEM URL in Internet Explorer, an error message box pops up: "500 Servlet jspservlet: unable to service request: Cannot find message resources under key org.apache.struts.action.MESSAGE".

Cause: The AEM program cannot access the URL directly (for example, http://hostname:portnumber/AEM/logon.jsp) without initializing .jsp files.

Solution: Access AEM at the URL http://hostname:portnumber/AEM (for example, http://localhost:9988/AEM).