This happens when you try to load a class from a local hard disk instead of a server, the class is not a subclass of Applet, and the directory where the class resides is not in the HotJava read path. The solution is to move the class file into a directory in the HotJava read path. On Unix one such directory is ~/public_html/classes (where ~ is your home directory). Alternatively you can change the HOT_JAVA_READPATH environment variable to point to the directory containing your classes directory.
Posted in: Java