While fighting with hotlink there is ONE big problem.

Nginx did not always correctly handle the allowed websites (such as feedburner images.google.com, etc.). Sometimes nginx redirects people to "nohotlinking.png" (see the code below) on the allowed websites and even on main website.

Any ideas?

The code:
location ~ \.(gif|png|jpg|jpeg)$ {
valid_referers none blocked server_names ~\.google\. ~\.bing\. ~\.yahoo\.
images.google.com ~\.feedburner.com;

expires 96h;
if ($invalid_referer) {
rewrite .* http://image-hosting.com/nohotlinking.png redirect;
}
}

After looking over the docs (see links below) , I would use wild cards instead of regular expressions if your needs are simple enough:

location ~ \.(gif|png|jpg|jpeg)$ {
valid_referers none blocked server_names *.google.com *.bing.com *.yahoo.com *.feedburner.com;

expires 96h;
if ($invalid_referer) {
rewrite .* http://image-hosting.com/nohotlinking.png redirect;
}
}


Based on what I read I would expect that to work fine.

http://wiki.nginx.org/HttpRefererModule
http://nginx.org/en/docs/http/ngx_http_referer_module.html#valid_referers
http://linuxsysadminblog.com/2009/08/using-wildcards-in-nginx-valid_referers/