It can be quite annoying if you have attempted to connect to a website and it is unreachable as windows remembers unresolved DNS requests. This can mean that the next time you attempt to connect to the site it fails even if the site is back up and running. This can also be a problem if you are trying to connect to other services such as FTP.
In Windows enter the command prompt – Start Menu >> Run type in cmd and hit enter. Enter ipconfig /flushdns at the command prompt as below as hit return
C:Documents and SettingsYour Name>ipconfig /flushdns Windows IP Configuration
Successfully flushed the DNS Resolver Cache.
Mac OS X Users
If you using Mac OS X then open the terminal and enter the followingOS X <= 10.5.1lookupd -flushcacheOS X >= 10.5.2
Linux UsersLinus users open up the terminal and enter the following$ sudo /etc/init.d/nscd restart
$ service nscd restart