Try this 1.
1) Click on Start --> In search box, type cmd and click on OK. Now enter this
ipconfig/all and press Enter.
Make sure that IP Address, Subnet Mask, Default Gateway and DNS Servers
are having addresses.
2) Internet Explorer :
Right click on the "Internet Explorer" icon---->Click on "Properties"---> Click on
"Connections" tab-->Click on LAN settings button. In that window uncheck all the
options, if you notice any option selected.
In Firefox, Click on Tools-->Options--->Advanced --> Network--->Settings--->
select "No proxy" option and click on OK.
If the problem still exists, try disabling either your antivirus or firewall.