How to repair: DNS error - Server cannot be found

If you try to open a web page and you get something like "Oops! This page appears broken. DNS Error - Server cannot be found." try this:

Open the CMD ("DOS") window: Click the Start button and write to the search line

cmd

and press Enter. A black and white CMD window appear. Write this to the CMD window:

ipconfig /flushdns

and press Enter.