I'm trying to edit the text that displays on the 'checkout_success >> text_message' page, to display something different when a customer purchases a product. However, when I click 'Save' I get the 403 forbidden error with the following details:
"Forbidden

You don't have permission to access /index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

I haven't had any other '403 Forbidden' errors in my admin panel, only when trying to edit the 'checkout_success'. I've tried setting the admin/index.php permission to 777 and also the admin folder to 777... but no luck, still the same error.