Hi

Thank you all for the suggestions and thoughts.

I did double check the nginx version I am having and it is 1.9.2.
root@ser2:~# nginx -V
nginx version: nginx/1.9.2
built by gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
configure arguments: --add-module=/tmp/nginx/ngx_http_substitutions_filter_module-master --add-module=/tmp/nginx/headers-more-nginx-module-0.26 --add-module=/tmp/nginx/ngx_pagespeed-release-1.9.32.3-beta --sbin-path=/usr/local/sbin/nginx --conf-path=/etc/nginx/nginx.conf
root@ser2:~#

but when I use the expires directive it shows invalid error same as before.
Seems like to get the feature I need to update the nginx version.

Thanks
Govind