ClassFormatErrors are used in the applet when the setup is not being properly set or the path to which the file is pointed is incorrect.

<APPLET

CODEBASE=http://your_server/webz/ns-home/classes

CODE=applets.myapp.class>

This happens due to change in the file format of CODEBASE in the Weblogic server. The Codebase tag should point to the HTTP server and not on the weblogic server. The path that is referenced by the CODEBASE tag is should not be the absolute directory path that is on the HTTP server and it should be configured properly to the Document root of the HTTP server. The above code should be changed with the code given below:

<APPLET

CODEBASE=http://your_server/classes

CODE=applets.myapp.class>