I wonder what is this?

[Rajeshwar Rao.V]

Error: 500
Location: /myCon/servlets/LogOn.htm
Internal Servlet Error:

java.lang.IllegalStateException: Can't happen - classname is null, who added
this ?
        at
org.apache.tomcat.core.ServletWrapper.loadServlet(ServletWrapper.java:261)
        at
org.apache.tomcat.core.ServletWrapper.init(ServletWrapper.java:289)
        at org.apache.tomcat.core.Handler.service(Handler.java:254)
        at
org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
        at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:79
7)
        at
org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
        at
org.apache.tomcat.service.connector.Ajp12ConnectionHandler.processConnection
(Ajp12ConnectionHandler.java:166)
        at
org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java,
Compiled Code)
        at
org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java,
Compiled Code)
        at java.lang.Thread.run(Thread.java:479)