Creates NullPreferences for use with applets. The system property java.util.prefs.PreferencesFactory should be set to org.das2.system.NullPreferencesFactory to use this class. System.setProperty( "java.util.prefs.PreferencesFactory", "org.das2.system.NullPreferencesFactory" ) doesn't work in applets--security exception. Also this works: java -Djava.util.prefs.PreferencesFactory=org.das2.system.NullPreferencesFactory ... I'm not sure where I found this solution originally, but here is a nice writeup: http://www.allaboutbalance.com/articles/disableprefs/