By using Google Analytics (http://www.google.com/analytics/), you can find pages on your site that could most benefit from website testing. See the video below:
This is the Google filter identified last October. This filter is for down ranking web pages in their result pages. I noted that many webmasters in online forums reported their experience on this aspect and still going on. Google applies this automated filter to some websites those are practicing spammy SEO techniques. The result is those websites downgraded by 30 positions.
Here are some quotes:
"I just got my site rank #31 on its own domain name and bunch of keywords/phrases I usually watch were bumped from #1 to precisely #31. Those #2 through #10 are sort of all over the map but generally within the first 60 results."
"I have this penalty on 2 sites and on both cases the site was hand checked by someone at Google and the next day it was dropped ~30 spots on all keywords. First site was 100% white hat, second site had too many affiliate links."
"I have a similar situation on my site. It's a PR 8 site that used to rank for just about anything I wanted. Then I added several hundred thin affiliate pages and all my rankings dropped from page 1 to page 4. I still rank #1 for my site name though. I also still rank high for specific searches in "quotes". I'm not sure what caused the penalty."
There are many things that can trigger this type of penalty. The only way to overcome this is to remove the spam elements from the site. You may verify whether the following techniques/methods that applied to your website:
1) JavaScript redirection
It might be considered as spamming. Rather than using this use 301 redirection by changing your .htaccess file. Read article
2) Guestbook/blog spamming
If you try to get links from guestbooks and blogs by spamming them then Google may applied this filter to your website.
3) Doorway pages OR Duplicate Pages
Remove those pages, Google doesn't like doorway pages. If you must use special landing pages for PPC ads and other ads, make sure that these pages cannot be spidered by Google and other search engines. You can use robots.txt to do that.
Try to remove the above spam techniques from your site. As this minus 30 filter is an automated filter, you will probably get your ranking back after some days.
Recently, I read in Matt Cutts' blog (Google Engineer), he is telling about cannonicalization of URL, which means the basic URL that should consider for google listing and ranking.
Normally, web developers uses several methods to link to the home page by www vs non-www, redirection, duplicate URLs, 302 'hijacking' etc. In most cases we can see links that are similar to the following, but going to the same page:
All the above links are different in technically and web server returns different contents for all those URLs. Here are some tips to solve this issue that Matt Cutts answered:
1) Do not place different versions of links throughout in your website.
2) If Google listed different versions of URLs, try to setting up 301 permanent redirection in web server.
3) Do not use the URL removal tool to get rid of these kinds of URLs.
XML