I'm not very good with these things but I'll try to explain it somehow. However what I say might be inaccurate 
Websites are located in servers that have ip-addresses (like 111.222.333.444 for example). Then you have domain names like pokerstrategy.com.
In the domain name server, there is a list of those domain names and ip-addresses so when you type a domain name into your browser it can link it to a correct server. DNS-error could mean that it doesn't find the server from the domain name server. But I'm not sure of that.
But anyway, when someone wants to block your access to a website, it is often done by removing the domain name from the domain name server. So when you type that domain name into your browser it doesn't find it and should take you to a blank site.
Maybe someone more wise can explain this better