Our website has built two years, website contents updated daily, but recently in Google on collected comparative less and less, who does know why is this?
one of the basic rule of search engine if you update you website content or meta information then you should update your site map also do it if you haven't did so far.
Very true. As far as Google is concerned, everything has to match up and if the new sitemap and maybe the robot text file isn't submitted either, you could lose a couple of pages being cached.