When embedding applets in internal web pages for moodle the applets will fail to load and run when using the Firefox web browser. Using a non-moodle external site the applets work fine within Firefox only within Moodle do they fail to load so I don't think it can be an imcompatibility with the Firefox implementation of/interface to the JVM.
I have tried both putting the JAR file in the course files as well as referencing an external JAR file on a remote server: in neither case does the applet run with Firefox. The browser simply states "applet not loaded".
Looking at the identical pages in the Safari browser everything works fine. The applets load and run perfectly in all the conditions.
The applet in question is linked below from the original website (not mine): the applet draws the electron wavefunctions for the hydrogen atom. I only have an active course site with the Moodle-embeded applet which does not have open access, sorry.
An example of the code I used to embed the applet is:
archive="qmatom.jar" width="600" height="50">
Sorry, you need a Java-enabled browser to see the simulation.
<param name="pause" value="10">
I put this in an internal HTML page within Moodle. This works fine with Safari and not at all with Firefox.
As a last gasp attempt to fix it I also changed the Moodle theme to see if that made any difference but it did not.