In Ubuntu 14.04 NginX is been compiled with the SPDY capability. To use it one must enable it inside the server {…} block for each virtual host.
eg.
server {
server_name mprofi.com www.mprofi.com;
root /var/www/mprofi.com;
index index.php;
#
# Added to handle HTTP and HTTPS and SPDY
listen 80;
listen 443 ssl spdy;
ssl_certificate /etc/letsencrypt/live/www.mysite.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/www.mysite.com/privkey.pem;
#
# ENABLE STRICKT TRANSPORT SECURITY and X-Frame-Options
add_header Strict-Transport-Security "max-age=63072000; includeSubdomains; preload";
add_header X-Frame-Options "DENY";
}

Restart NginX
service nginx restart