Sounds like your ISP is having issues. If it's your ISPs DNS servers you might be able to add DNS servers from another domain.
Google DNS Primary / Secondary: 220.127.116.11 / 18.104.22.168
You could add AT&Ts DNS servers, plus a few extra DNS servers to a longer list instead of just using the Auto option.
It usually doesn't take too long to reset, reboot the DNS servers so you could just wait till it clears up.
Possibly a problem with the Telco equipment. That type of stuff usually clears up too but it might take a bit longer.