You can't. No more than you can make a garden last 500 years without people tending to it regularly. Digital has a lot of great advantages, but permanence isn't one. Will DNS even be used in 500 years? Maybe. Will whatever hosting provider you use still exist. Almost definitely not. Will html and css and javascript still be used even? Or will they be something academics study the way we study latin and greek today?

Books, buildings, and art survive 500 years and not much else.