2
You have to access your site via FTP or cpanel filemanager or whatever way you normally acess the files on your site and change the permissions on mainfile.php to 444 its probably at 777 or something right now, basically your changing the permissions so its not world readable or writable.
Ask you host if your not sure how to change file permnissions.
Or if it's installed locally on your computer browse to mainfile.php right click it select properties and make it read only.
Michael Jackson = King Of Pop
Xoops = King Of CMS