Error:
nginx: [emerg] invalid parameter „http2“ in /etc/nginx/sites-enabled/mainpage:3
nginx: configuration file /etc/nginx/nginx.conf test failed
mattionline:/etc/nginx/sites-available# nginx -v
nginx version: nginx/1.6.2
Solution
Your nginx version must be at least 1.9.5 for using the http2 feature.
Update your nginx version. If you use debian for example you must install nginx through a third party repository, because in the official debian repository there isn’t a newer nginx version with http2 support.
