after installation of iRedMail it overwrites my etc/nginx/default.conf. now it looks like this . my main www folder is in var/www. i tried to change but after i getting this errro . see at bottom

upstream php_workers {
server unix:/var/run/php-fpm.socket;
}

HTTP

server {
listen 80;
server_name _;

root /var/www/html;
index index.php index.html index.htm;

location / {
    root /var/www/html;
}

# Normal PHP scripts
location ~ \.php$ {
    include fastcgi_params;
    fastcgi_pass php_workers;
}

# Redirect webmail/SOGo/iredadmin to HTTPS
location ~ ^/mail { rewrite ^ https://$host$request_uri?; }
location ~* ^/sogo { rewrite ^ https://$host/SOGo; }

location ~ ^/iredadmin { rewrite ^ https://$host$request_uri?; }

# Deny all attempts to access hidden files such as .htaccess.
location ~ /\. {
    deny all;
    access_log off;
    log_not_found off;
}

# Handling noisy favicon.ico messages
location = /favicon.ico {
    access_log off;
    log_not_found off;
}

}

HTTPS

server {
listen 443;
server_name _;

ssl on;
ssl_certificate /etc/ssl/certs/iRedMail.crt;
ssl_certificate_key /etc/ssl/private/iRedMail.key;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

index index.php index.html index.htm;

location / {
    root /var/www/html;
}

# Deny all attempts to access hidden files such as .htaccess.
location ~ /\. {
    deny all;
    access_log off;
    log_not_found off;
}

# Handling noisy favicon.ico messages
location = ^/favicon.ico {
    access_log off;
    log_not_found off;
}

# Roundcube webmail
location ~ ^/mail(.*)\.php$ {
    include fastcgi_params;
    fastcgi_pass php_workers;
    fastcgi_index index.php;
    fastcgi_param SCRIPT_FILENAME /usr/share/apache2/roundcubemail$1.php;
}

location ~ ^/mail(.*) {
    alias /usr/share/apache2/roundcubemail$1;
    index index.php;
}

location ~ ^/mail/(bin|SQL|README|INSTALL|LICENSE|CHANGELOG|UPGRADING)$ { deny all; }

# Normal PHP scripts
location ~ \.php$ {
    include fastcgi_params;
    fastcgi_pass php_workers;
}

# iRedAdmin: static files under /iredadmin/static
location ~ ^/iredadmin/static/(.*)\.(png|jpg|gif|css|js) {
    alias /usr/share/apache2/iredadmin/static/$1.$2;
}

# iRedAdmin: Python scripts
location ~ ^/iredadmin(.*) {
    rewrite ^/iredadmin(/.*)$ $1 break;
    include uwsgi_params;
    uwsgi_pass unix:/var/run/uwsgi_iredadmin.socket;
    uwsgi_param UWSGI_CHDIR /usr/share/apache2/iredadmin;
    uwsgi_param UWSGI_SCRIPT iredadmin;
    uwsgi_param SCRIPT_NAME /iredadmin;
}
# iRedAdmin: redirect /iredadmin to /iredadmin/
location = /iredadmin {
    rewrite ^ /iredadmin/;
}

# SOGo
location ~ ^/sogo { rewrite ^ https://$host/SOGo; }
location ~ ^/SOGO { rewrite ^ https://$host/SOGo; }

# For IOS 7
location = /principals/ {
    rewrite ^ https://$server_name/SOGo/dav;
    allow all;
}

location ^~ /SOGo {
    proxy_pass http://127.0.0.1:20000;
    #proxy_redirect http://127.0.0.1:20000/SOGo/ /SOGo;
    # forward user's IP address
    #proxy_set_header X-Real-IP $remote_addr;
    #proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    #proxy_set_header Host $host;
    proxy_set_header x-webobjects-server-protocol HTTP/1.0;
    #proxy_set_header x-webobjects-remote-host 127.0.0.1;
    #proxy_set_header x-webobjects-server-name $server_name;
    #proxy_set_header x-webobjects-server-url $scheme://$host;
}

location ^~ /Microsoft-Server-ActiveSync {
    proxy_pass http://127.0.0.1:20000/SOGo/Microsoft-Server-ActiveSync;
    proxy_redirect http://127.0.0.1:20000/Microsoft-Server-ActiveSync /;
}

location ^~ /SOGo/Microsoft-Server-ActiveSync {
    proxy_pass http://127.0.0.1:20000/SOGo/Microsoft-Server-ActiveSync;
    proxy_redirect http://127.0.0.1:20000/SOGo/Microsoft-Server-ActiveSync /;
}

location /SOGo.woa/WebServerResources/ {
    alias /usr/lib/GNUstep/SOGo/WebServerResources/;
}
location /SOGo/WebServerResources/ {
    alias /usr/lib/GNUstep/SOGo/WebServerResources/;
}
location ^/SOGo/so/ControlPanel/Products/([^/]*)/Resources/(.*)$ {
    alias /usr/lib/GNUstep/SOGo/$1.SOGo/Resources/$2;
}

}

errror.log

2015/02/22 09:05:22 [crit] 14782#0: *4 connect() to unix:/var/run/php5-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 109.255.139.76, server: richmondgardens.ie, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "richmondgardens.ie"
2015/02/22 09:05:22 [error] 14782#0: *4 open() "/usr/share/nginx/www/50x.html" failed (2: No such file or directory), client: 109.255.139.76, server: richmondgardens.ie, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock", host: "richmondgardens.ie"
2015/02/22 09:06:17 [emerg] 14843#0: "user" directive is not allowed here in /etc/nginx/conf.d/default.conf:1
2015/02/22 09:07:52 [emerg] 14869#0: no "ssl_certificate" is defined for the "ssl" directive in /etc/nginx/conf.d/default.conf:36