How to Fix '403 Forbidden' Errors

The error "403 Forbidden" comes from the Apache web server when either

a directory was requested but the directory does not have an index.html or index.php file,
the permissions on the requested file or directory do not allow it to be read by the web server, or
the permissions on one of the directories in the path have been incorrectly customized and are preventing Apache from accessing anything contained below that directory.

If you also see the following message at the bottom of the "403 Forbidden" error page:

Server unable to read htaccess file, denying access to be safe

the problem is likely one of the following:

The permissions on the app's .htaccess file don't allow it to be read by the web server.
The permissions on the app's public directory don't allow Apache to see if there is a .htaccess file.

In each case, you can find more details about the specific problem by looking in the app's Apache error log located at

/srv/users/serverpilot/log/APPNAME/APPNAME_apache.error.log