If you do not have a index file (index.html, index.htm, index.php, etc.), it will display the Forbidden error. If you are getting this error when viewing your domain, please upload a index file into the /public_html/ folder.
The most common reason for this error is because the URL was typed incorrectly. If the URL is correct, be sure that the URL is using the correct letter casing. All file and folder names are case senstive, ie. index.html is not the same as Index.html.