gatsby-pingbot/src/pages/404.js

import  React from "react"
import { Link } from "gatsby"

import "../css/base.css"

const NotFoundPage = () => {
  return (
    <>
      <title>Not found</title>
      <h1>Page not found</h1>
      <p>
        Sorry we couldn’t find what you were looking for.
        <br />
        <Link to="/">
          <button className="blue-buton">Go to home page</button>
        </Link>
      </p>
    </>
  )
}

export default NotFoundPage