If you get "cannot resolve domain name" errors in your browser or your sites are not loading and you see "Resolving host..." status then most probably you have a problem with DNS servers. DNS server is short for domain name server - a server responsible for translating textual domain names to specific IP addresses on the network. For example when you type www.google.com in a browser address line your browser doesn't know where to get home page of google.com domain until it can query DNS server and get exact IP address where to send a request.

Typically default DNS servers are provided by internet provider and will work most of the times. But since each provider maintains its servers differently there is a relatively high chance that DNS server will malfunction for short period of time. During this period you won't be able to access any services on the internet which use DNS servers. This includes all functionality of internet browser. To avoid such malfunctions you can change default DNS servers to ones provided by Google or Open DNS. These servers are maintained in a very scalable and reliable fashion and there is very low chance they will go offline.

Google DNS IP addresses:

 

8.8.8.8

 

8.8.4.4

 

OpenDNS IP addresses:

 

208.67.222.222

208.67.220.220

For instructions on how to change your DNS servers read corresponding article on this or other related websites.