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.

For Mac OS X 10.10 Yosemite Use This Tutorial

In Mac OS X 10.9 Mavericks

Open up your terminal Application located in Applications/Utilities/Terminal

Mac OSX Terminal

Enter this command:

dscacheutil -flushcache

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.