OS X 10.11 El Capitan uses the same command as the previous version of OS X to clear the DNS cache. You need to open a Terminal window and enter:
sudo killall -HUP mDNSResponder
It will ask you for your password if you do not already have elevated privileges.
If you’ve moved a site somewhere and still don’t seem to be seeing the correct output after doing the above, it might be worth clearing cached pages from your browser.
To do this in Safari, click on Safari on the top menu, select Preferences and go to the Privacy tab. From there you can either hit the Remove All Website Data button to clear all your cookies and caches or click on the Details button and search for the specific site whose data you want to remove.