In protest of SOPA, Wall Street, irresponsible government leaders and bankers, Anonymous plans to take down the 13 DNS root servers on March 31st. These are the main servers responsible for knowing what domain goes to what IP address all the time.
How it works is that when you type something like, flesheatingzipper.com into your browser, your ISP looks up the IP address and sends you on your way. ISP’s are getting this information from the root servers located around the world. These servers hold the information that connects domains to IP addresses. Most ISP’s cache this information on their servers but usually only for a couple of hours.
So what would happen if you tried going to a website and it didn’t know the server IP? It would look like the error above and won’t be very fun. Anonymous outlines more how it will work here (pastebin). “The very fact that nobody will be able to make new requests to use the Internet will slow down those who will try to stop the attack. It may only lasts one hour, maybe more, maybe even a few days. No matter what, it will be global. It will be known.”