1. If you are getting the "java.security.AccessControlException", this means you should sign the applet before using it in a browser. See "How to sign Java applet" tutorial.
2. If you are getting "java.lang.NullPointerException at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel (Unknown Source)", this means that the Java VM cannot find some of dependent classes (Class-Path problem).
For an applet using Active Query Builder Java Edition, you should specify a reference to the ActiveQueryBuilder.jar in the jar file's manifest. For example:
Class-Path: lib/ActiveQueryBuilder.jar
Also you may specify it in the "archive" attribute of the <applet> tag:
<APPLET code="appletdemo/QueryBuilderApplet.class" archive="AppletDemo.jar,ActiveQueryBuilder.jar" width=800 height=600></APPLET>

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