Most websites from 2000 are gone - only stored on the Web Archive, if at all
What I think you meant to say is "websites that were around in 2000 and have since vanished" - some websites are still around today that were started in the 1990s, but of course today they look nothing like how they did in 2000 or even the previous decade.
Actual examples are CERN (first ever website from 1992, still around today), Bloomberg and IMDb, both launched in 1993, followed in 1994 by Fogcam (still around today, was threatened with closure but survived), the BBC and Microsoft.