We should update DNS records after we had registered a domain name and did setup web hosting for that domain.
DNS is heavily cached and changes could take up to 24 hours to take effect. It is recommended you wait this long after the initial set-up before troubleshooting any errors. DNS changes could take up to 24 hours to take effect. It is recommended you wait this long after the initial set-up before troubleshooting any errors
Refresh Local Computer DNS Cache is a step to troubleshoot DNS setup
1. 
In OS X Leopard, open Terminal application from the Utilities folder in the Applications folder and type in “dscacheutil -flushcache” (without quotes) and hit enter.
2. 
On Windows, go to Start > Run > type “cmd” (without quotes) and hit enter; Then type in “ipconfig /flushdns” (without quotes) and hit enter.