Usually dns (domain name server) not enabled. The dns change addresses like "yahoo.com" into a ip address of the sere e.g. 192.1.168,24.
Without a dns you cant access a web page.
To see if you have dns set up in windows go to...
...start>run> type cmd and press ok. On the prompt screen type ipconfig/all
Scroll down for dns and it should have a address like 192.168.1.254.
If it doesn't then you need to set up a correct network address.