I was running localhost (Apache 2.4.6) but only the
index.php was openable in the web browser. The subdirectories were returning 403 Forbidden error.
Now, I added the permissions according to this answer. For reference, these were the permissions:
sudo adduser <username> www-data sudo chown -R www-data:www-data /var/www sudo chmod -R g+rw /var/www
Accordingly, the folder in which I placed all the content of the website became owned by
www-data group. And although I've added myself to the group, I cannot open the folder!
(But the subdirectories have become accessible from the web browser.)