There might be problem with your DNS servers of ISP. A computer by default uses ISP DNS servers. You can manually configure your DNS servers. It is free and usually better than your ISP.
Go to Control Panel -> Network and Internet -> Network and Sharing Centre
Click on Change Adapter settings.
Right click on your connection icon (Wireless Network Connection or Local Area Connection) and select properties.
Select Internet protocol version 4.
Click on “Use the following DNS server address” and type either of the two DNS given below.
Google Public DNS
Preferred DNS server : 126.96.36.199
Alternate DNS server : 188.8.131.52
Preferred DNS server : 184.108.40.206
Alternate DNS server : 220.127.116.11