Documentation section gives an error of 502 with offline message:
This page (https://docs.nopcommerce.com/display/en/Setting+up+Payments) is currently offline. However, because the site uses Cloudflare's Always Online™ technology you can continue to surf a snapshot of the site. We will keep checking in the background and, as soon as the site comes back, you will automatically be served the live version.
Where is a snapshot of the site?