Cause: For Web Preview from the Builder to work the Registry variable FORMS_JAVADIR must point to the location that contains the Java files. This variable should should have been set by the Oracle Installer when Oracle Oracle Forms was installed. A typical value for this variable is c:\orant\forms\java.
Action: Create or update the registry variable on NT, FORMS_JAVADIR, and set its value to the location that contains the Forms Java files.