If you are reading this it means that the server problems that have caused everything to become invisible for a couple of days have been resolved.
Apparently there was a technical issue involving a conflict between different parts of the internet as to on which server green-history.uk was actually located. Various "name-servers" (the computers that tell other computers like the one you are reading this on where to find a particular website) got messed up during a server upgrade.
It all serves to remind us how in a complex system that is designed for resilience (eg the internet or our own eco-system), a small change can sometimes have unexpected consequences. Of course the internet is nowhere near as complex as the whole earth ecosystem but the analogy is apt. Two small parts of the internet (our nameservers) were locked in conflict and so the rest of the system simply isolated and bypassed them. Hence Green-History.uk disappeared for a couple of days. In the same way ecosystems build themselves to be able to deal with minor disruptions in one part by isolating and working around them.