Protect your bandwidth whenever possible. By adding a few lines of code to your root level .htaccess file you can prevent external websites from directly loading your images, audio, and video files.

Add the following code to your .htaccess file:

RewriteEngine on
RewriteCond %{HTTP_REFERER} ^$
RewriteCond %{HTTP_REFERER} ^http://www.?your-domain.com/.$ [NC]
RewriteRule \.gif|jpe?g|png|mov|avi|wmv|mpe?g$ - [F]

[AaronHalford.com]