nginx

# /etc/nginx/sites-available/www.example.com.conf
server {
server_name www.example.com;
listen 443 ssl;

root /usr/share/nginx/www/;

ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;
ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;

sub_filter_once off;
sub_filter "Welcome" "Sello";
}

server {
server_name www.example.com;
listen 80;

root /usr/share/nginx/www/;

access_log /var/log/nginx/access_www.example.com.log;
error_log /var/log/nginx/error_www.example.com.log debug;

sub_filter_once off;
sub_filter "Welcome" "Hello";
}

# Links
http://wiki.nginx.org/Configuration
http://wiki.nginx.org/HttpSubsModule
http://wiki.nginx.org/NginxHttpSubsModule
https://www.nginx.com/resources/admin-guide/restricting-access/
http://openresty.org/en/