In many cases when web user or blog admin can receive the message that “403 Forbeiiden error – You are not authorized to view this page”. I have search for the solutiona and provided my best here:
If your account is hosted on a Windows server it could be a problem with the Directory Indexes. The default configuration of the server is to load index.htm, index.html, default.htm, default.html, default.asp files at highest priority.
WordPress is done in PHP so the default page is index.php. Now this is not part of the default configuration so we need to add it in directory indes and gie it a highest priority to load at first.
You can do it either from the hosting control panel web site settings derectory indexing option or you can contact web hosting service provider.