You may have an issue with the
DNS configuration on your computer.
Try to browse to this URL:
http://144.81.82.80
If `nslookup` can't find the IP address for
http://www.ets.org, then you won't be able to browse to it.
You will either need to fix your DNS configuration or you can create a quick workaround by adding an entry to your C:\WINDOWS\system32\drivers\etc\hosts file.