The new Java Plug-In supports disabling of the "class loader cache" via a new parameter to the applet, object and embed tags:

  <PARAM name="classloader_cache" value="false">

This functionality needs to be documented publicly. Note that this capability does not imply the same level of specification as a public API; it is more of an implementation detail, similar to "codebase_lookup", which is documented at http://java.sun.com/javase/6/docs/technotes/guides/plugin/developer_guide/special_attributes.html .

Engineering specification for feature:

http://j2se.sfbay.sun.com/web/bin/view/Deployment/NewPlugInClassLoaderCacheSpec