Unable to determine IP address from host name

When I am connected via pppd to the Internet, I still get on a clients's
browser this error message:
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The requested URL could not be retrieved

While trying to retrieve the URL: http://www.ibm.com
The following error was encountered:
Unable to determine IP address from host name for www.ibm.com
The dnsserver returned:
Name Server for domain 'www.ibm.com' is unavailable.
This means that:
 The cache was not able to resolve the hostname presented in the URL.
 Check if the address is correct.

Generated Mon, 17 Jan 2000 22:28:44 GMT by num (Squid/2.2.STABLE1)
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Where do I have setup DNS (I think, that's the solution)? In the
etc/ppp/options or somewhere else?
Received on Mon Jan 17 2000 - 16:08:52 MST