Something very strange happened on October 20th. Possibly you may have noticed it, although it’s also quite possible it passed you by as a perfectly uneventful Wednesday.

But on 20th October a huge number of website owners and SEO service providers saw their websites plummet down the search page rankings, taking their traffic figures with them as they dived down towards the murky depths of Google’s backwater (otherwise known as page 2 onwards). So what happened?

It seems that Google changed one of its algorithms slightly. It’s important to appreciate that Google doesn’t use one single algorithm, but a massive number of highly complex algorithms all working together. Just a small tweak to one algorithm can easily cause massive changes in the search rankings, as it did on this occasion.

On their support forum Google’s John Mu confirmed that many of these rank changes were likely to be due to an algorithmic change, and that as a result of this change websites may be assessed slightly differently from previously, affecting their rank position.

Importantly John Mu went on to confirm that the changes to site listings was not a penalty imposed because of spam, black hat SEO, underhand tactics or technical issues with the content. You can hear more about this in an earlier videoby Matt Cutts at Google:

One of the interesting points raised in Matts video is the fact that he mentions that “various parts of our algorithms can apply to sites at different times.” What does this mean? Basically it means that at any time in the future your site may cross a threshold for one of Google’s algorithms, which suddenly means that your site is being assessed quite differently. Of course, this could be good news. Or not.

However, on this occasion it was a huge number of websites, including many top ranking websites, which got hit in one single fell swoop, suggesting that this was the result of an algorithmic change. But what does this change tell us about the new algorithmic structure?

Obviously no one outside of Google can ever hope to unravel the intricate workings of Google’s vastly complex algorithmic structure, and Google remain tight-lipped when discussing it, but there was a very interesting, if not downright unsettling phenomenon noticed by many of the webmasters and SEO service providers whose sites got hit.

Because it seemed as though the websites replacing theirs at the top of the search results included a number of somewhat dubious websites. Whilst a few of those listed at the top had every right to enjoy a top position, others seem to have achieved their status by using underhand tactics, spamming, websites created by scripts rather than people, black hat SEO driven sites and even sites without content. So what’s going on?

Again, Google is keeping quiet, but it’s perfectly possible they got it wrong. Yes, even the mighty Google has made plenty of mistakes in the past, as it becomes ever more complex even the slightest change can have wide spreading repercussions which may go far beyond their original intentions.

So does this mean that we’ll be seeing more changes soon? Possibly. Could this mean a sudden boost in a site’s ranking? Maybe. Should we start using black hat methods, spamming or other dubious tactics? Definitely not. Should we continue to produce high quality, user oriented content which people find genuinely useful? Definitely. Remember, search rankings can go up as well as down.