Thank You, For your information. This could really help many who are feared of decrease in PR.
Keep Sharing.

There can be many reason, 2 reasons i will tell:

1) The update of content is the first thing that can affect your rank. Suppose, if you were doing 10 posts on your blog and suddenly you it decreased by 7 it will results in less.

2) Second thing is that continuity in off-page activities should be must if you want to be always on top. You are not the one who is trying to top search engines. So, if you concentrate on these points you will definitely see some change in PR and SERP results.

Reasons:
1. Bad neighborhood links.
2. Irrelevant links.
3. Linking under hidden internal pages.
4. If the pages are static and with no updation.
5. Many more outbound links.

Originally Posted by shruchi nagar

The SEO experts all over the web have been battering their gums about the massive effects that update has made to rankings and pointing to all sorts of dramatic changes that they feel have been made to the algorithm.
The sites that are being badly affected have been using techniques such as:
• Doorway pages
• Hidden text
• Multiple domains
• Buying links
• Accepting off-focus reciprocal links from other sites
• Working with link farms and link exchange schemes
• Using various cloaking techniques
• Using duplicate content on different domain names
If your rankings on Google fell over the last month, you website has probably been affected by this ranking algorithm change.
Change in the Google ranking algorithm
Google wants to make its search engine results pages more relevant by removing some of the spam. It seems that the following elements are the most common reasons if your Google rankings dropped:
• hidden text on your web pages (especially text that is hidden in invisible CSS layers)
• paid links or other links that are considered outside of Google’s quality guidelines
• overuse of internal links or anchor text as the sole source of optimization
What if website ranking have dropped?
If you were guilty of any of the above, and you lost positions, stop doing it, apologize to Google and ask them to have another look at your site, once all the black hat techniques have been removed from your site.
• If you use CSS on your web pages, search for style sheets that might be interpreted as spam attempts.
• Make sure that you have links from the right web sites. While it is not important that if a link is a reciprocal link or not, it is very important that the links are from related sites.
• Do not overuse the same keyword in links to your web site. Use different keywords so that the links to your website look natural.
If your web site rankings on Google have dropped, don’t panic and follow the tips above. Chances are good that you’ll get your high rankings back.

yes i completely agree of your tips but i want know that keyword stuffing, cloaking, door way page what mean and can you explain now..