Here are some reasons why your page may be unavailable.
1- Domain name not yet resolved. (can take 48 hours or more)
2- Incorrect DNS entries in your registra control panel
Also check that your mainfile.PHP has the correct site URL. If you created your site using a temporary username/ IP this needs to be changed to your proper domain name once it resolves.
Make sure your web host has supplied you the correct DNS data
Try to reach your site using your temporary username/ip