How can you tell why you were dropped in the SERPs?

don't request anything to google until they mail your about spamming.....serp can be down for many reasons. The following things are most famous:
Outbound link is higher than inbound.
Inbound links from not niche site.
Inbound links from spammy site.
You Suddenly stopped SEO
etc.

**serppagerank.com did not provide me right place of my keyword.

Google has been doing so many ranking updates that it is hard to tell which one may have affected your site.

The biggest issues today are:

1. Duplicate content - The content on every page must be unique.
2. Poor quality content - Spun content and junk content no longer work
3. Poor quality backlinks - Any links that you bought in bulk are likely to be crappy links. Google has been attacking link building sites for years. Most directory links are useless.
4. An overall poor quality site - Too many unrelated articles and too many outbound links can get a site flagged as a blog network site.
5. Too much SEO - Keyword stuffing, hidden text, or just about anything that Google does not like.

Don't expect Google to tell you what is wrong with your site with a reconsideration request. They usually want you to tell them what you have corrected when you submit the request. A reconsideration request will not do anything unless you have changed something that could be affecting the rankings.

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