DNS
Human beings like to use names and words. Computers use numbers. When you want to browse a website you enter its human-readable name into the browser address bar. The computer has to convert that to the numeric address used across the Internet between your computer and the web server.

A DNS (Domain Name System) Server provides the numeric address when your computer asks for a human-readable address.

To check your settings:

Open the "Start" menu
Open "My Network Places"
Open "Network Connections"
Right click on the connection to your cable modem and choose "Properties".
Open the "General" page. Select "Internet Protocol (TCP/IP)", then click on "Properties".
Enable both "Obtain an IP address automatically" and "Obtain DNS server address automatically".
Click "OK" to close the "Internet Protocol (TCP/IP) Properties" window.
Click "OK" to close the "Local Area Connection Properties" window.