What is the viral Kamala Harris 404 page that even Donald Trump Jr posted about: 'Unburdened'

Republican commentators circulated a purported Kamala Harris 404 screenshot and claimed that the White House did that mocking the former vice president. But the screenshot was not from the White House's site but apparently from Kamala Harris' campaign website. The viral image referenced the former Vice President's favorite phrase 'unburdened'. Harris is currently considering future political moves, including a potential presidential run in 2028.