It is an excellent way for a newbie to learn the basics on how Google crawls, indexes, ranks and shows their search results. But how is this useful for an SEO junky like yourself? I'll outline the parts I find useful to more savvy SEOs and webmasters.
See Examples Of Spam Pages Removed From Google:
My favorite part is that Google is showing me real examples of spam pages pulled from their index within the past couple hours. You can see those examples on this page and Google told us that these are recent examples of pages that "appear to use aggressive spam techniques such as automatically generated gibberish, cloaking and scraping content from other websites." Before clicking and looking at them, you should be warned (by Google) "these screenshots are generated automatically and are not manually filtered. While uncommon, you may see offensive, sexually explicit, or violent content."
In fact, I should have a page shortly that archives all of these examples for you to look back at historically. I'll share that page when it is done.
Here is my favorite sample spam page I've seen recently:
Brian White, a spam fighter at Google, put it nicely:
Charts Of Manual Actions By Category, Reconsideration Requests & Notifications
Google has told us plenty of times the percentages and numbers of manual actions, reconsideration requests and webmaster notifications they have sent out. But they never plotted that data for us, that is until now. I'll selfishly take credit for it (kidding) but I did ask Matt Cutts a few years ago if they could build these graphs out. I am not sure if I was the first to ask...
So what did Google tell us with these charts?
Manual Actions By Category: This graph shows the number of domains that have been affected by a manual action over time and is broken down by the different spam types. Google says only 0.22% of domains had been manually marked for removal.
The types of spam documented here include pure spam, legacy, hacked site, unnatural links from your site, automatically generated content, and infinite spaces, cloaking and/or sneaky redirects, thin content with little or no, added value, unnatural links to your site, parked domains, user-generated spam, hidden text and/or keyword, stuffing, spammy free hosts and dynamic, and DNS providers. You can learn more about these over here.
Reconsideration Requests: This chart shows the weekly volume of reconsideration requests since 2006.
Webmaster Notifications: This graph shows the number of spam notifications sent to site owners through Webmaster Tools since 2010.
Now plot these charts against penalties you may have received to make yourself feel better and maybe to figure out how to fix an issue?
Published Google Quality Rater Guidelines:
Finally, Google themselves decided to publish the PDF document of the quality raters guidelines. This document has been leaked so many times, I guess it just made sense for Google to publish it.
What changed? Matt McGee covered that over here.
So those are the three things I would pull out as being most interesting for SEOs and webmasters to look at.