Thank you so much for your reply
I added cache-control header in httpd.conf file as below
Header set Cache-Control "max-age=604800, public"
Following filters are enabled for the PageSpeed module. Since one of the images was 25 MB, I had to increase value for the property ModPagespeedMaxCacheableContentLength and the PageSpeed module seems to be processing this file. Is there a way to compress this huge image to a smaller size and send it to the browser. I also used height and width attributes for the <img> tag here http://220.127.116.11/
and was expecting it to render a smaller image in terms of dimensions and file size but does not seem to be working.
Thank you for your help.