If this occurs it is generally for one of 3 reasons.
1. You don't have a properly named default page in your main /public_html/ directory. Acceptable file names are listed below: index.htm index.html default.html index.sht index.shtml index.cgi index.php
2. The /public_html/ directory permissions are improperly set. When you receive your account the permissions are correctly set. Contact us to fix this.
3. You put a .htaccess file in your main /public_html/ directory, or you changed the configuration of an existing .htaccess file which is locking up your web site.
4. You should contact support if you are not sure what's causing the problem