Testing And Experimenting Is (Or At Least Should Be) The Backbone Of Any SEO Strategy.
Most professional SEO companies and experts routinely conduct formal and informal SEO experiments, some of which are generously posted online for education and calibration purposes. At SEO.com, we encourage our employees to build and monetize personal websites when they're not at work, as an opportunity to innovate, test, and take risks that we can't with our client campaigns at work.
Now I'm sure this post will attract a lot of scientific method purists that insist that 99% of these tests are invalid because they were conducted in uncontrolled environments, or didn't account for all possible external variables, etc. And they would be absolutely right, but I respond with a paragraph from John Quarto-von Tivadar's MarketingLand post, mainly because I couldn't have said it better myself:
Ever hear the adage, “Anything worth doing is worth doing wrong”? It’s a great way to think about testing and improvement of any kind, because it deals with the fact that the first step toward improvement always “feels” the hardest. It speaks to the moment when you’re most susceptible to false objections like “It’s too complex!” or “That’s inefficient!”
In my opinion, these studies are incredibly valuable and interesting, and should be read and understood with a conscious understanding that they are not examples of perfect science. They're "helpful" observations, that in most cases increase our understanding of the science of SEO and its best practices, even if they're not scientifically sound.
- Do Capital Letters Affect SEO
- Google Plus SEO Experiment
An experiment dealing with the effect of +1s on ranking URLs.
- Life After Penguin
Ian Howells walks through some interesting findings regarding pages that have been hit by Penguin.
- SEO Experiment with Non-Link References
- Testing the Effects of Negative SEO
- Recovering from the Penguin Update (A True Story)
Nick Eubanks depicts the effects of switching exact match vs branded anchor text.
- Diversity of Anchor Text Test (testing the Penguin update)
- SEO Experiment: Google Image Search
- Geolocation Results with Generic Searches (Google)
- Guest Blogging Outreach Test
Brilliant post analyzing effectiveness of various methods of guest blog post outreach.
- Testing the 1st Link Priority Rule
Christian Greiner Follows Up on SEOmoz's 2008 test regarding anchor text attribution.
- 6 Extreme Canonical Tricks
- Schema Examples
Although not titled as an SEO test, Craig presents some examples and screenshots of the result of testing some Schema attributes.
- A Quick Experiment with Google+
- Eye Tracking SERPs Test
- HTML Link and Image Attributes
- Testing the Value of Hyphenated vs Non-Hyphenated Domain Names
- Which Type of Anchor Text is Most Effective?
- Title Tags - is 70 Characters the Best Practice?
Cyrus follows up on David Naylor's 2010 experiment proving Google indexed at least 213 characters of title tags.
- An Experiment in Boosting Google Rankings w/Search Volume
- How Tweets Influence Search Rankings
- SEO Experiment: NoFollow Links DO Pass Value & Rankings in Google
- Whiteboard Friday - We Bought Links, and It Worked
- Local SEO Experiment - Google's Change Location
- How Many Page Title Characters Does Google Index?
- Why Targeting an Indented Listing May Be a Bad Idea
"Indented" listings are a little out of date, but I would be interested to test how/if it's changed for double listings in 2012.
- Keyword Rich Internal Anchor Text - How Much is Too Much?
- Testing the Value of Anchor Text Optimized Internal Links
- First-Link Anchor Text Attribution
Rand confirms that only the first link in the source code, pointing to any other specific page on the web, actually passes any anchor text attribution. So don't think you're helping your home page by linking with "cheap gifts" in your footer, after you've linked to your home page 3 times already.
- First Link Counted Rebunked
SEO Scientist Rebunks SEOmoz's tests on first link anchor text attribution.
This list is certainly not complete, so please be as generous in the comments as these professionals were kind enough to post their findings for our benefit in the first place, by adding any tests you've conducted, or that you feel will complete this list (to date).