Dizzy - If you are on a Unix flavored box running Apache just drop this into your .htaccess file and place it in a directory that you want to protect or in your root to protect the whole domain...
Make sure to change the url's in the code accordingly...
RewriteEngine on
RewriteOptions inherit
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://.*domain.com/.*$ [NC]
RewriteRule .*[Jj][Pp][Gg]$|.*[Gg][Ii][Ff]$
http://www.domain.com
Best Of Luck
