The Dead End of the Iberia Riddle

The infamous fourth riddle of the Seisen no Iberia bonus track website, while seemingly like the others, is different in one important way: it has no answer. Whatever is put in the answer field, the visitor is redirected to the same error page. It's not even done through JavaScript, although such a function is defined in the main.js file - instead, the button after the answer field is not even a button, but a direct link to the error page. There is absolutely no way to proceed from the riddle to any other page than the error one. There's not even any hidden server-side code that could be triggered - it's a static HTML page that does not make any kind of request to the server except through the link to the error page. No <form>, no Ajax. To sum it up: it's a complete dead end. So, what now? If the expected route doesn't work, the only choice is to look somewhere else. But where? The earlier riddle pages and their branching alternate pages and error pages h...