site not accessible from certain locations

Hi, I was following the following page for help.
https://wordpress.org/support/topic/website-not-accessible-to-some-users

mine(http://namastheandhra.com) is a dedicated server from godaddy and users are complaining that they are not able to access the site sometimes.

is there any specific filters in wordpress that stop access from certain locations if accessed more?

any ideas how/where to start the investigation?