On June 11 2013, Matt Cutts made an announcement "We just started a new ranking update today for some spammy queries". This update was worldwide and many porn websites, mobile websites, spam websites, etc saw a heavy cut down in their ranking and disappeared from search results.
This update targets spam queries like payday loan, pornographic and mobile websites. It has impacted 0.3 to 0.5 percent of English queries. It is a work in progress and will be completely rolled out in coming 1 to 2 months. The cut down in other languages on these websites are even heavy because the number of spammy websites is more in this language.
Sites that re-direct users to unrelated pages and blank pages with nothing on it but ads are being heavily punished. Google believes these redirects are intentional and are unethical that cheat viewers and users.
Mobile websites following the same strategy in smartphones are also being heavily punished.
By punishment Google means that their ranking will go down and will be shown below in search results and some spammy websites will be blocked even. Websites having virus are also being punished.
Google is becoming stricter day by day. Penguin 2.0 which rolled out on May 22, 2013 affected 2.3% of English queries and targeted paid linking, duplicate content and keyword stuffing. There too spammy websites saw a decline in their ranking and now with this update against spammy query Google is fighting against porn websites and mobile websites.
Now that most of the people around the world are using smartphones for search and everything, websites have developed a new way around to cheat Webmaster. If you have such websites and have seen the ranking goes down and search visibility disappear, you have to stop all the spammy tricks. Finding new trick won't help as Matt Cutts has said that Google will be becoming stricter day-by-day and would provide only quality results to their user, playing along the guidelines is the only way to be in long run.
Recommend the tutorial