Here is a trick to change DNS servers. This change is not necessary this change is for netbies which want to experience fast internet.
To change DNS servers first of all you need to be root user.
First open Terminal in the terminal type following lines.
su -
sed s/nameserver.*/nameserver\ 156.154.70.1/g -i /etc/resolv.conf
here 156.154.70.1 is DNS servers which mostly use.
when you type "