I'm guessing that you didn't provide a complete URL. In that case, if you define a "hellopage" in web.xml the page you indicate with the hellopage will be served if no explicit page is named.
Some people, when well-known sources tell them that fire will burn them, don't put their hands in the fire.
Some people, being skeptical, will put their hands in the fire, get burned, and learn not to put their hands in the fire.
And some people, believing that they know better than well-known sources, will claim it's a lie, put their hands in the fire, and continue to scream it's a lie even as their hands burn down to charred stumps.