DNS cache keeps an IP address stored in your computer. If you’re doing web development and you’ve moved your content to a new server sometimes you can’t reach it. The DNS entry needs to be changed.
In Mac OS X 10.9 Mavericks
Open up your terminal Application located in Applications/Utilities/Terminal
Enter this command:
Then, to reload DNS type this command:
sudo killall -HUP mDNSResponder
Now, ping the domain that was cached and the new IP should show up for you.