Ask your ISP's technician what is the Domain Name Server IP. He will certainly give you that ip number, it is a must under the contract. Then, for example, you are given such number as: 88.888.888.88 and your ISP's domain, say, is called forsale.corporation.com you will simply do this in the terminal:
echo "88.888.888.88 forsale.corporation.com" >> /etc/resolv.conf
Then restart the internet protocol or network manager.
Launch firefox and see if it can travel now from west to east
HOpe that helps.