nginx: [emerg] "server" directive is not allowed here

If I test nginx.conf file with:

nginx -t -c /etc/nginx/nginx.conf

I can recieve:

nginx: [emerg] "server" directive is not allowed here in /etc/nginx/nginx.conf:89
nginx: configuration file /etc/nginx/nginx.conf test failed

In my situation I really wanna work with nginx virtual host configurations which is located:

cd /etc/nginx/sites-available