Little .htaccess help

[cd34]

RewriteEngine on
RewriteCond %{HTTP_REFERER} ^http://(.*@)?([a-z0-9-]+\.)*firstdomain\.com(:[0-9]+)?(/.*)?$ [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://(.*@)?([a-z0-9-]+\.)*seconddomain\.com(:[0-9]+)?(/.*)?$ [NC]
RewriteRule .*\.(asf|mpg|mpeg|wmv|avi|rm|gif|jpeg|jpg|zip)$ - [F,L]

the ! in the prior rules means, if it DOESN'T equal the following.

In this case, you remove the !, the rules have an implicit AND, but, you want an OR, so, if it matches firstdomain OR seconddomain, block.