Abidon

Hi guys, I'm about to sign up for a Basic Plan. I already have a .com.au domain registered, but when I enter my domain name, Hawkhost doesn't have an option to choose .com.au. How do I go about this? Also, although I'll be building and running the site. My client, whose business I'm making the site for, will be doing all the payments and registration. That wouldn't be a problem, right?