Suddenly several sites rapid drop in Google

None of that is strange. Sites get dunked all the time.
Do you think amazon.com ranks that page when one is
searching for fuzzy slippers, or do you think the page on
fuzzy slippers ranks?

Main keyword is a misnomer, sitewide that is. Individual pages
rank, not an entire "website." I would say upwards of 95% of
my google traffic is to subpages, not the main index page.
Makes sense to me. I can't be the only only. Just like the
amazon example above. Unless people are searching for
amazon.com, they mus be searching for something that
requires a product page, not the main page.

You rely on google for your business, and you say google is lost?

Google is under no obligation to ever show any of your pages,
in the past, now, or in the future.

Due to many rather multifaceted updates that google does, your
pages could have been hit for any number of reasons.

I would vote for anything that deemed your content just not
suitable anymore.

No, this does not mean I think google can detect great content.
What they can do, is detect content that is just not needed
as much as another site's.

Big difference. That why unique, hand written content means
virtually nothing in and of itself.

Paul

very similar situation i faced too just 10-15 days ago my fb page which was ranking on top google page gone and its nowhere to find in 22pages

I just don't know what is going on. Currently I am in situation like never before, since I am unable to find a reason why 4 of my sites dropped like this. And, to be more interesting, when I type my homepage with http in Google, it appears nowhere, but my subpages do. I can get my homepage in Google only if I type site:mydomain.com . Whats the issue ?

several sites,?

Are you using the same GA and GWT accounts for all sites?

Yes, I am aware it is some sort of penalty. Nothing in Webmaster Tools in Manual actions for now. As far as I figured out (with help from some friends) it is because I used same anchor text for linking in 75 % of my backlinks. I will change this easily and see what would happend, I suppose I am on the right track.

Ok, I finally found out why my sites had drop in Google. On all of that sites I was using the same wordpress theme. It seems (according to experiments) that something in wordpress theme was causing my drop. Because on one site I put another wp theme and my site went back up to his usual place in Google in a less than 24 hours ! On other site I changed wordpress to AV Arcade Script and that site also went back up to Google in its usual position in a less than 24 hours. After I realise that something in wp theme was a cause for this huge drop, I changed themes on all of my dropped sites and all of them recovered sucessfully.
So this is a warning to WP webmasters. Always change the theme first, and then look for another cause of the problem, if you have a google drop, like I had.
Cheers !