Most users don’t need to use this command, but it’s very helpful for web developers and network admins to troubleshoot issues with web sites.
This command is run via terminal.
On Leopard (10.6) and Snow Leopard (10.7):
(as root or admin user) dscacheutil -flushcache
On all other version (10.0 – 10.4):
(as root or admin user) lookupd -flushcache