I am using netgear modem I couldn't get access to Yahoo page or oassportindia.gov.in page coul any one help me now I am also not getting access to 198.168.0.1

First verify that you have Internet, by connecting directly to the modem.Once you can surf without the router add the router and connect via a wired connection, Restart the computer and router then run ipconfig from the command line, the Default Gateway address is the address of he router. Type this address into a browser and check the configuration of the router. Your router should be set to supply IP addressed to connected computers.
If you r router was used and the configuration changed you should be able to find info on how to reset it to factory settings on the manufactures website.