What Are Search Engine Penalties?
There are, in a broad sense, two types of search engine penalties, and Google can impose them in two ways. The types of penalties are as follows:
Total: Your site is completely dropped from the search engine. It’s no longer in the index, and the search engine will probably stop visiting your site. (This is often called de-indexing or a ban.) Assuming that you’ve been penalized (and your site can be dropped for reasons other than a penalty), you’ve really annoyed Google!
Partial: Your site is still in the search engine, but it just doesn’t seem to be ranking well; plus, some other symptoms are appearing that also suggest a penalty. But the site is still in the Google index, and Google even returns periodically to crawl more pages.
This is still bad, of course, but not as bad as a total ban. Google’s saying, in effect, “We don’t like what you’ve done, but we’re willing to give you another chance.” Phew!
By the way, a partial ban probably has different grades, different “levels” of penalty. In fact, the SEO community has come up with all sorts of names, such as a –30 penalty (Google adds 30 positions to your site every time it comes up in the search results, pushing it down three pages); a PageRank penalty (Google reduces your PageRank); a –950 penalty (you drop so far that you just can’t be found); and so on.
Google almost certainly has some kind of obscenity filter that is intended to drop porn sites from the regular results and that says, in effect, “We’re not going to drop you from our index because you haven’t necessarily done anything wrong, but we don’t want your site coming up for regular search results.”
These penalty types are conjecture, though — Google doesn’t state what the penalties are, beyond saying, in effect, “Yes, we penalize, and we have different grades of penalty.”
Now, the two processes by which a penalty can be imposed are the following:
Algorithmically: The Google “algorithm,” the complex piece of software that evaluates sites and decides how to rank them, has found something on your site egregious enough to penalize your site.
Manually: Google has a “webspam team” that employs real, live human beings to examine websites. If the team finds something it doesn’t like, it can impose a penalty.
Relatively few sites actually get penalized; in fact, if you pay attention during your travels around the web, you’ll find all sorts of sites that really should be penalized. These are sites that play all sorts of nasty SEO tricks yet somehow are still in the index. Why?
First, with a trillion or so pages in the Google index, there’s simply no way to manually examine all of them for spamful intent. On the other hand, to automatically or algorithmically apply penalties, search engines have to create a very loose system that penalizes only the very worst offenses, or they are bound to penalize innocent sites.