as @gandalf458 says there is no IF statement in plain HTML. So if it is possible on the system you are using it will be using a serverside technology.
Can you see any files with .php at the end instead of .html? (or maybe .asp, .jsp or .cfm).
If you can't see any you could try and create a page called info.php and inside that put
<?php echo phpinfo(); ?>
Upload that to your server and see if it loads in a browser. If it does you are running PHP. Once you have tested delete that file off your server.