Applet won't run from GlassFish, Incompatible magic value. Runs fine from OS X web server

For a programming assignment, I am trying to have a GlassFish server serve up a client applet to talk to the server servlet. I've been stuck on having GlassFish deliver the applet. I have been searching extensively on this, and am not finding anything that resolves the issue - though I am learning quite a bit.

I have a 'hello world' applet compiled to tskApplet.class.

import java.applet.Applet;
import java.awt.*;
public class tskApplet extends Applet {
    public void paint (Graphics g) {
        g.drawString("Hello world! It's an applet!", 5, 25);
    }
}

I have an html page that loads the applet with the following applet tag:

<applet code = "tskApplet.class" width="300" height="300"></applet>

I've tried (to no avail) all sorts of variations such as putting the .class file in a .jar and including archive="tskApplet.jar" in the applet tag, and using a .jsp page, etc.

I'm using IntelliJ and if I run the tskApplet from an applet run/debug configuration it works fine. I followed this guide to set up GlassFish with ImtelliJ: http://wiki.jetbrains.net/intellij/Developing_applications_for_GlassFish_Server_in_IntelliJ_IDEA

If I copy the exact same .class file and .html file from the GlassFish server's web directory to the OS X Sites folder, then the applet works fine from the browser when I access it that way.

But if I run GlassFish and access my web application, the applet does not run. Instead I get these errors in the browser java console:

java.lang.ClassFormatError: Incompatible magic value 1768779887 in class file tskApplet
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:219)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Plugin2ClassLoader.java:249)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:179)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:160)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Plugin2ClassL开发者_运维问答oader.java:674)
    at sun.plugin2.applet.Plugin2Manager.createApplet(Plugin2Manager.java:2990)
    at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1481)
    at java.lang.Thread.run(Thread.java:680)

Any suggestions where to look next?

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Sounds like GlassFish is running with an older JVM than the Applet was compiled with. Find out what JVM the server is running.