TNP has built-in protection to protect your account's hits usage (so that
no unauthorized users use your code and use your allowed hits). We do this by
allowing you to add / remove allowed referring URLs directly from your account.
For example if you will be using the thumbnails code on your site called abc.com,
then you can add it from your account and if later you want to also use it on
def.com, you can add it easily as well as remove them if you don't want those
sites using your code later on.