Help! DNS Server error on a Mac???

Hi!

I've encountered a problem while trying to enter my beloved Facebook account, Every time I try and log on I get the following message,

Network Error (dns_server_failure)

Your request could not be processed because an error occurred contacting the DNS server.
The DNS server may be temporarily unavailable, or there could be a network problem.

For assistance, contact your network support team.

Its been like that for 2 days!!!

I've had a look around and the only advice on the problem seems to relate to windows, any Ideas of how to sort it if I'm using my Mac?