When you add a domain name in your hosting control panel you have the option to add an Instant alias. An Instant alias is a temporary domain issued by us and used to allow access to your web site or mailbox during DNS propagation. We use the domain name instantlink.co.uk as our alias i.e. http://demodomain.co.uk.instantlink.co.uk
If you create your instant alias and then browse to it straight away you may get an error. Although the DNS record creation is instant it can take a short while for the outside world to pick it up. You browser can then cache that result and it may appear that you then can't access the site. The solution to is to clear your DNS cache on your computer.
On windows you need to do the following.