gecko-dev/extensions/xml-rpc/test

Create a chrome/test/content directory and place xml-rpc.xul in that dir. Then
fire up Mozilla with -chrome chrome://test/content/xml-rpc.xul.

Fill in a number between 1 and 50, and click the button. A XML-RPC server,
courtesy of Userland software, will tell you what US state it thinks goes with
that number.