I read an article that talked about the "Dreaded Google Slap".
If you’re new to SEO or Search Engine Optimization, you may be asking: "What is a Google Slap"? I don't like the term because it implies that Google randomly punishes you for no reason. Google is in business - they want to provide the best search results they can. If they just decided to move a highly ranked site from the 1st page of results to the 39th, with no reason, people would not get the same quality of search results, which would make people use others search engines instead of Google. They're not going to jeopardize their business just to mess with your site's rankings.
It is true that once in a while Google will adjust the algorithms used for ranking. When they do this, some sites that previously ranked well for certain search terms, or Keyword phrases, may no longer rank well for those same terms. When this happens, those affected will complain that they've been "Google Slapped".
This not only happens with "Organic Search Results" (the non-paid listing of sites you get when you type in something to search for), it can also happen to paid advertising. PPC (Pay Per Click) paid advertising shows up on the Right Side of the Google search results. When this happens with PPC, you can be dropped for a keyword, or your bid amounts can go up drastically.
On most of my sites, I've had my rankings drop and then return after a day or two to exactly where they were. Maybe Google changed something and realized it was a mistake and fixed it. Maybe it's just part of their algorithm to "cycle" some sites around to see what happens with click-through. This is not the same thing as getting "slapped". The rankings returned pretty quickly and were not buried. When you're "slapped" you don't bounce back in a day or two, you're gone!
What about BlackHat?
When Google finds that people are "gaming" their system and getting sites to rank higher than they should, they update their algorithms to counteract whatever "trick" was being used. If you have quality content, follow my advice, and don't try to cheat, then you don't usually have to worry about getting "slapped", delisted, or otherwise ignored by Google.
Search Engine Optimization