After getting really excited about CloudFlare, I was setting it up for a client’s WordPress site when it disappeared during a DNS update. The CloudFlare-served error told me that the web host wasn’t serving data to web traffic, which seemed odd.
The web host was HostGator (shared reseller account), and a chat technician confirmed my suspicion: they do not (yet) support IPv6 mapping that CloudFlare provides. So if you’ve enabled the IPv6 feature from CloudFlare’s settings and your site suddenly disappears, make sure your host supports the IPv6 protocol. Disabling the feature (it’s just a feature you can disable!!) restored the blog to its happy former state. That is all.