Yesterday my site completely dropped from google cache. Backlink is still fine but with site:www.abcd.com shows nothing. Until yesterday it was maintaining top ranking with the most competitive keywords and last PR update it got PR 5. Today my site is nowhere. Is it something that I have to worry about it or it is just temporary problem?
It may just be a temporary thing. One of my page 1 sites disappeared yesterday but has just turned up again in it's normal place.
I see some sites do this every now and then. If you did not do any blackhat seo work you should be fine.
Sometimes the google bot refreshes its data, since there are multiple data centers and a complex algorithm involved certain parts of the indexing go offline for a certain period of time. At least this is how it was explained. Google also removes some garbage sites from the mix when this happens. Of course the algorithm is ever changing so nobody really knows exactly how it works.... at least that's my understanding from what I've read on the subject.
I had 3 sites drop out on Monday night. They still aren't back. Let me know when and "if" your site pops back in so I can make the firm decision that I am royally screwed!
All my 3 sites have been dropped in last 2 days. There are many other sites that have lost lots of indexed pages lately.
Just to add, no probs recently with my site that is steady position 7 page 1 google for most important keyword.
Exactly same thing happened to two of my websites exactly the same day as it happened to you. I think there was some technical error in Google. My site completely dropped from index. It is back in index, but nowhere to find for important keywords.
yesterday site:mysite.com had 10.000 pages Today is 14.700 BUT, yesterday SERPs: 3 - 10 Today: 40 - 50 I still don't understand why....
it appear that google are changing something in their logarithm ... some of our sites was massivly desindexed
It seems that quite often when people here complain about a huge drop, there sites are somehow spammy or greyhat. So I will say quite often I am happy about the updates. Hopefully that isn't the case for you, but I don't have any idea about your sites. Would you consider your sites whitehat and useful for users (not just mfa, etc...) ?