Looks very nice. I would just suggest you to explain things a bit better as people will be confused with your current signup system. It says for example: Enter prefix and Choose subdomain (where it lists alv). While it is clear to someone who knows how things work, it is very hard to understand for someone who looks for web hosting for the first time.
A simple legend like Ex: you.subdomain.com and listing the actual sub domain name like example.com instead just example would make things much friendlier
![Smile](images/smilies/smile.gif)