I could not track down the reason why my domain names occasionally are inaccessible to some visitors. With some I mean some, not everyone. I was working on my website, and at some moment I could not access it anymore. I thought that it's a hosting-related problem. I was getting "website not found" error in my browser. In the same time I could still access the website from a different computer (with different ip address). Problem was gone the next day when I woke up, so unfortunately, I let it go and did not try to find out the reason behind it.
Right now myself and some of my course mates were not able to access our website while some others were able to. Website is now inaccessible to people which it was accessible to earlier.
I was looking through error logs and anything that could be of use in Cpanel. But I was kind of lost.
I don't have extensive knowledge about servers. Which means my reasoning can be faulted. I thought that some visitors could theoretically get ip-banned if they download/upload a lot in a short amount of time. I thought that some defensive mechanism to prevent "spamming" could have worked. However, when I looked in Cpanel I saw that no ip addresses are banned.
Using google made me come across the idea that the problem could be caused by ISP and their DNS service. I found out it is possible to use specific DNS servers, instead of "obtaining DNS server addresses automatically". I changed settings of my connection (specifically, Internet protocol version 4 ) and now I can access my website again. I 'm using opendns.com nameservers now.
This means I have found a fix. But I still don't know why the problem happens in the first place. I shouldn't be asking visitors of my website to change settings of their internet connection.
So, the question is: Why does this happen, and how can I prevent it? If I can?
Edit1: Records in my registrar look like this:
Type IP Hostname Alias MX Preference NS ns3.website.com NS ns4.website.com