question about direct access to url

hi my question is about displaying a friendly message when someone directly types a url in the browser. example i have one file called form.php which processes the information entered in the form and lets say the next page is thankyou.php?firstname=david by seeing the url if someone types thankyou.php?firstname=smith in the address bar the browser will display smith. 1. so if a user enters a url in the browser directly to a specific page("thankyou.php") i would like to display a message like = "Direct access to this file is not allowed" 2. with the above method assuming even if i type thankyou.php in the browser directly, though i own the file i will also get the message "Direct access to this file is not allowed". so i would not like to see this message, i guess for this i need to specify my IP address i suppose. please provide answers for 1 and 2 points above. thanks.