If your domain name service (DNS) servers are not working properly (or you simply want to use another DNS server setup), you can change what DNS servers are used on your Mac in the Leopard operating system.
Instructions
Difficulty:
Step 1
Click the "Apple" system icon in the upper-left corner of the screen, click "System Preferences" and then click "View."
Step 2
Click "Network" and then click "Show."
Step 3
Select the "Airport" section and then click "TCP/IP" to open the TCP/IP section.
Step 4
Type in the DNS server IP addresses that you want to use and click "Apply Now."