It doesn't look like there's an error. You just have debugging switched on which is why messages are being written to the error log.
The Forbidden message looks like something to do with file permissions or Apache configuration and the additional 404 error means that you have Apache set up to display a custom 403 (Forbidden) page but Apache can't find it.
The Forbidden message looks like something to do with file permissions or Apache configuration and the additional 404 error means that you have Apache set up to display a custom 403 (Forbidden) page but Apache can't find it.