Change the domain name on line three to your YOUR domain. Leave that
slash in there, it's very important. This line allows you to link to
your own images.
Now, save the page as .htaccess (If you are using a Mac, you should
leave the dot off the beginning and add it when you upload the page.
Rename it on the web server, otherwise you won't be able to see the
page once you've saved it because the Mac makes any page beginning with
a period invisible).
Upload this page in the root (main folder) of your website. If your
site already has an .htaccess file, you can add this information to it.
What this will do is simply prevent all your images from being
hotlinked. You could also add a line to redirect to a different image
but, since bandwidth theft is what you are trying to prevent, that's
never made too much sense to me. There are a lot of good tutorials
explaining this method online. Google: prevent hotlinking .htaccess