Sometimes when you add a new domain on a cPanel web hosting account and try to visit the site your domain might be redirected to a page like yourdomainname.com/cgi-sys/defaultwebpage.cgi As far as I can figure this is a 301 redirect in cPanel hosting, so unfortunately it can be remembered by your ISP, your OS and by your Browser.
In such cases try waiting for a couple of hours and clearing your browser cache. It has worked for me. So most probably if you clear your browser cache, you will also be able to open your domain without getting redirected to this mysterious /cgi-sys/defaultwebpage.cgi page.
If clearing the browser cache doesn’t work or your customers too complain of this issue and you can’t make them clear their browser caches, then you might need a more advanced fix from the server side. I found a couple of articles explaining the process here and here.
I don’t know exactly why this happens but I think this is something to do with trying to access our newly setup domain before the propagation delay has properly set-in. The browser cache keeps a copy of this default cgi page and keeps showing it for hours or even days after.
It has happened to me couple of times. Sometimes, I have setup a static website or installed WordPress on that domain. Sometimes, when I go to a page like mydomainname.com/wp-login.php it loads normal but when I go to mydomainname.com it still redirecting to /cgi-sys/defaultwebpage.cgi Sometimes when I have tried opening the same domain with another machine or mobile phone this domain redirect doesn’t happen.
Hope clearing the browser cache works for you. Feel free to share your experiences and post any other solutions that has worked for you in the comments below.