403 Error on Pages

403 Errors imply Unauthorised Access. While authentication is handled by IIS, authorisation is controlled by SharePoint. However, HTTP Error codes and messages are raised at the IIS level. A 403 error is usually due to incorrect Application Pool settings. You need to ensure that all applications and virtual directories within your Portal use the same Application Pool. If you are using a custom app pool, also make sure that the Service Account is valid and the password hasn't changed.