site disappeared Overnight wrt Rankings in Google

Till August 13th, i did had a decent SERP in Google, but the next day morning all of the sites disappeared from the top places. No where in the top 20. The Keyword which has very low competition was in the 1st position earlier. But today, even that disappeared from the rankings. Even the blog results disappeared overnight. What could be the reason?

Does the web hosting has any role in this? Say if the google crawls the site when the sever was down for maintenance reasons, will it cause this sort of adverse effect?

That was the issue when Google Webmaster tool reported that the site has been crawled on Aug8. But today when i checked out the same, the last crawled date was on Aug13. Interestingly from Aug13th onwards, I'm facing this problem.

Last week may be on Aug6th or so ... i've changed the images in my site to noadware-free-anti-spyware-download-graphic.jpg from noadware.jpg

Is this anything to do with the fall of SERP? Except this change i've nothing added or deleted.

Please help me in this regard. Thanx in advance.

This happened to me when I changed all of my urls, and it took about 2 weeks to get back to it's normal position.

Unless you have been sandboxed for whatever reason or lost all backlinks this should just be a temporary thing

The site is indexed. All the back links are present.

The change of the images should not have big impact, unless the traffic you would receive was from Google Images.

Did you made any other change within this month? Like linking to some new site, or changing the URL of the pages? Apart that, many other sites have faced this issue with Google's new algorithm, one loses rankings someone else gains.

Something similar happened to mine. The reason was duplicate content and it was just like a paragraph. So check for that. Also, make sure you don't have like 40 link exchanges. I've also been penalized for that, and as soon as I removed most the links my rankings went up again.

One reason not mentioned here yet is the recent update to the PR system that Google has been conducting. During these days you can see your site serp drop and then once update is complete you will notice it suddenly jump back to its original position or even higher. It does not always happen, but has been seen a few times over the past year or so. Normally with this you see it come back in about a week or two, but of course in the mean time if you have a popular site it can mean a lot of lost traffic.

I would concur with hostnetric as when the PR export takes place it is done on a data center to data center basis and when the PR export is done one is able to see the stable results of their sites and hence you are experiencing varios results for your site. I hope they will be fine soon.