I just had a very strange thing happen. Our company website became unavailable for about half of the workers in office. However, it is visible from any computers/iPhones from outside.
I tried to clean out cache, reset Internet connection, assign a different IP, reboot the PC, etc.
The ones that cannot see will not get better, and mean while other machines have no trouble seeing this website.
The error message is simply "this site cannot be displayed", no security warnings, nothing.
I tried PC, Mac, iPad, IE, Firefox, Chrome, Safari, and they all seem to to fail for some users.