Apple’s core networking for OS X (Lion, Mountain Lion, etc) is famously poor. One of the (many) unfixed bugs is this:
“I go to a webpage (e.g. google.com) and my browser displays a message saying ‘Server not Found’. If I keep hitting Refresh, it never works. If I wait a few minutes and try again, it works”
This is entirely Apple’s fault. They aggressively (and incorrectly) cache “failed” lookups. And … because it’s Apple … you can’t turn it off. It’s been broken for at least 5 years now, which suggests they have no intention of fixing it.
But: you can “flush” it. Since it’s a cache (which are designed to auto-flush anyway), there’s no harm in doing this.
Solution: restart Apple’s DNS cache
- Open a Terminal window
- type: “sudo killall -HUP mDNSResponder”
- (you’ll need your admin password, annoyingly, because you’re ‘forcing’ Apple’s code to behave itself)
- Reload your webpage – works immediately
After the first time, you can repeat the command frequently without typing your password. Simply hit the “up” arrow (to re-type previous command) and Return to run it.