If you have only recently registered or transferred your domain name, it can take up to 72 hours for the changes to completely propergate across the internet (though usually it is much sooner), during this time your site will be unavailable at the said domain.
To preview your site before this happens, it is possible to create a "temporary preview domain" that will allow you to view your site in advance.
- Log into the control panel
- Click the Domains icon
- Select the domain you wish to setup the preview URL for
- In the information box, click the Click here to create a temporary access URL link
- In the following screen, click the Setup button
- Your site will then be given a temporary URL which you are able to use instantly and will be shown to you in the resulting box.