Any reasons, why google is not indexing the website pages. previously the pages was more but not the indexed links are decreasing. any suggestions.
yes you should check your internal link structure. use help of some tool to check internal links. you can check this with help of Google Webmasters Tool as well. And keep changing something in your pages and try to build some links.
When was the last time the was cached? In past months, Google somewhat slowly decreasing showing backlinks for sites, mostly you can see more of your backlinks on google webmaster tool account..
Use social bookmarking sites for a faster indexing, i recommend folkd.com since whenever i post my content there is indexed really fast and appears on google first page.
Google must have indexed pages earlier. Then run a duplicate pages check test on your website. It must have found the same and de indexed it. I have faced this problem earlier also, so what I am telling is because of my previous experience. I suggest that you focus on Unique and Quality content focussed towards your Niche and you will see more and more pages getting indexed in Google and hence much traffic and thus enhanced revenue for your site.
It is normal for Google to drop pages from the index, this trend will grow as tons of pages are added on a daily basis and Google have struggled with capacity issues for many years. This article explains it a little better http://www.businessservicesuk.com/businessarticle/Are_Google_Struggling_107
Update your content regularly. Engaging on deep linking and creating a sitemap helps your sub-pages get index. Build links. Back links helps your site get index as well.
As I can see you're already banned, but I would say by building a site map(Google loves it) and may be pinging the new content right after posting it. Also better PR guarantee you faster bot crawl.
First of all, How old is your website and what is your RANK (not pagerank but rank on alexa) And do you know the story about Prince Google and King Google? This little story will help you about understanding why your website, your links, your post appear in google and sometimes disappear. It goes something like this: The story is, when your rank is below (I am basing in alexa) your site, your post, will always be indexed by PRINCE google only. What prince google does is analyze your website, examine, scrutinize it if your post is unique (no duplicates) etc and pass it to king google. this process is quick even 2-3 depending on the current rank of your site. during those days, you will be happy you are seeing your post or your website in the google listing. Once Prince google pass your website to KING GOOGLE. Some of your post will disappear or your new website will disappear (due to the fact your ranking is way LOW) this is normal and this happen to all people. The remedy? - Frequent post (1 post a day keeps google spider stay - Keep doing it at least you make a good rank in alexa (I think below 1,000,000 rank will make an "observable" stickiness to google caching) - Once you are in that rank, KING GOOGLE will cache your page not prince google. Why? because you already have the authority. Benefits of being cached by King Google? No more disappearing of your post or website. P.S: Disappearing of my post happened quite often to me before, especially If I am having a head to head post with same niche stories like sites in mashable, cnn etc. Example: (Michael Jackson died) If you post a story like that. You are competing with millions of story around the globe. If King Google is not the one "caching you" I am sure tomorrow or the next day, your story will not appear in google anymore. How do you know if your post disappear? Try this search in google If you saw your postno1 on the result. Then it's still alive otherwise, it's not cached by king GOOGLE. meaning you dont have the enough authority yet so it disappeared. Does this makes sense? (pardon for for some redundancy)