Your Java Chat works fine, Jon.
I believe the main problem is that most people don't have Java Script enabled on their Browser.
If you're using Internet Explorer, then here's how you do it:
First, click on the "Tools" tab. Next, you go to Internet Options.
Inside there, click on the Advanced Tab.
Next, find the Microsoft VM heading. Underneath it, you should see three Boxes:
Java console enabled (requires restart)
Java logging enabled
JIT compiler for virtual machine enabled (requires restart)
Make sure all three boxes are checked, and then click Apply.
If you have problems after this, I'm unaware of how to fix them.