ErrorDocument 403 Apache Server
Rectify your standard web server 403 error ( here viewing : f_unblocked.htm )
  . . . in a few related pages here is how to customize from Client's side a standard web server 403 error response.

Insert the following access data to surf the demo : Login=pinco - Password=pallino
All files in directory extra , except f_blocked.htm ,  are http retrievable ...check : self.jpg - index.php
The following Content of .htaccess returns a 403 Server Standard Error :
# .htaccess ( basic code )
<FILES f_blocked.htm>
order deny,allow
deny from all
allow from 123.45.67.89.
</FILES>
<Files .htaccess>
Order allow,deny
Deny from all
</Files>
...if you add to your .htaccess file the ErrorDocument Code ... as is , you would then let your Clients read what you want instead of a standard 403
← User=pinco - password=pallino
Rectify the standard 403 server response
PHP referer : IP Client 123.45.67.89. can access f_blocked.htm in http mode
(...the red dot here above (.) is a useful jolly-char )