(This is adapted from some different articles from SEO MOZ, Designshack and WebPro News. I just wanted it available online in a format that was easier to read for clients. It’s also turning into a general web history.)
2000 – Google Toolbar launches with its own page ranking. Sites begin to bounce up and down in the Google rankings unpredictably, which began to be called the Google Dance.
“Boston” 2003 February – Google was still rolling out algorithm updates and index refreshes on a monthly basis. Sites that backlinked each other take a hit while sites that constantly update and have many incoming links are promoted.
“Cassandra” 2003 April – Addressed hidden text, hidden links and linking between sites owned by the same owners.
“Dominic” 2003 May – Google did a deep crawl of the web, and reported backlinks changed.
“Esmerelda” 2003 June – Instead of updating their index monthly, Google began updating it more often. I speculate that the Supplemental Index got its start here. Basically, Supplemental Results is where Google put your web pages if they didn’t think they were terrible or great. Key website phrases are used to rank pages.
“Fritz” 2003 July – The index now changes daily.
“Florida” 2003 November – Old tactics like keyword stuffing were now penalized and made SEO an industry. White hat websites (those who follow guidelines) are given some promotion.
“Austin” 2004 January – Invisible text and meta keyword stuffing were cleaned up.
“Brandy” 2004 February – Google begins looking at anchor text, link neighborhoods and synonyms. Google’s stock price doubles in August.
“Nofollow” 2005 January – Nofollow tag introduced.
“Allegra” 2005 February – Sites changed rankings but the specifics were unclear. It was meant to remove high ranking spam from the index.
“Google Local” 2005 March – Google launched its Local Business Center.
“Bourbon” 2005 May – Google announced 3.5 updates but it was speculated that this involved how duplicate content and the www subdomain was handled. Google also swicthed to new datacenters.
“Sitemaps” 2005 June – XML sitemaps can now be submitted, letting webmasters tell Google what the important pages on a site were.
“Personalized Search” 2005 June – Google taps your search history to adjust your search results.
“Gilligan” 2005 September – Unclear change but Google confirmed that the index data was updated daily while Toolbar was only updated every three months.
“Google Maps and Business” 2005 October – Google merged Maps with Local.
“Jagger” 2005 September-November – A series of updates targeting linking practices and made Pagerank updates public.
“Big Daddy” 2005 December-Feb 2006 – Cleaned up Google’s handling of urls and linking, though some websites suffer needlessly. Also, Adobe bought Macromedia with its Dreamweaver and Flash technologies.
“Supplemental Index” 2006 November – Google stops labeling results as Supplemental, which are neither great nor terrible.
“Universal Search” 2007 May – News, images and more are now viewed in search results.
“Buffy” June 2007 – A group of minor changes.
“Dewey” April 2008 – Results shuffled but no clear factors reported.
“Suggest” 2008 August – As you type your Google query, Google now offers suggestions on what you are typing.
“Vince” 2009 February – Big brands become favored in search results.
“Canonical Tag” 2009 February – Lets search bots know about pages without affecting humans.
“Caffeine” Summer 2009-Summer 2010 – Big infrastructure improvements, resulting in quicker indexing and ranking.
“Real Time Search” December 2009 – The most recent Twitter results are shown in the search rankings.
“Places” April 2010 – Google Local & Maps become Google Places.
“May Day” May 2010 – From late April into early May, long tail traffic drops for sites with thin content and improves for others.
“Brand” August 2010 – Instead of showing only one page from a website in a batch of ten results, Google now allows the same domain to show multiple times.
“Instant” September 2010 – An improvement on the suggest feature.
Social Media Integration October 2010 – Bing integrated Facebook Likes, photos and such into its search results. Google integrated Twitter Tweets, too.
“Previews” November 2010 – Searchers can now see a webpage thumbnail before they visit the site.
“Social” December 2010 – Social signals are officially being used to modify search results.
“Brand Penalties” January and February 2011 – Overstock and JCPenny were penalized due to black hat tactics.
“Panda” February through June 2011 – Sites with lots of content but little value, lots of ads and other visitor quality issues were penalized every month ~ about 12% of websites. Even individual penalized pages can drag down a website that was otherwise ranking well.
“+1 Button” March 2011 – Google account holders can click the +1 button to show their approval of web pages or Google ads. This will affect search results.
“Schema” June 2011 – Data like addresses are now encouraged to be formatted by Schema.org’s preferences for more standardized search engine indexing.
“Google +” June 2011 – Google’s most successful social media application launches, with 25 million users within 5 weeks of launch. Business brand name accounts are deleted, though there are plans for these kinds of accounts. There is also a big Google push for using your real name, much like Facebook’s insistence to do the same.
“Another Panda” July 2011 – Site rankings change but no major updates are announced.
“More Sitelinks” August 2011 – Sitelinks expanded from 8 to 12. Adobe released Muse, a potential replacement for Dreamweaver. Adobe also released Edge, which helps create HTML5 web animations.
Panda 2.4 and Analytics Changes August 2011 – Panda was rolled out across the globe, with the exception of a few countries. Google Analytics now counts every keyword visit as a new visit, which should eliminate the zero-views-zero-pages visits being recorded in Analytics. (http://www.seomoz.org/blog/panda-24-and-analytics-session-update-rolled-out-simultaneously)
Scraper Changes August 2011 – Google put out a call for users to submit known scraper websites so the algorithm can be made to detect them. However, Google can only detect who published their content first. So if your site posts something and it gets copied by another site, your site may be seen as the Scraper if Google crawls the other site first.
Blogger Gets A Makeover August 2011 – Google made improvements to the back end of Blogger, making it more user friendly.
PDFs in Search Results and Subdomain Internal Links September 2011 – Google posted answers about how PDFs are treated in search results. They’re just like web pages, although images currently aren’t indexed. Subdomains like www.domain.com and subdomain.domain.com will have its internal links included with domain.com. (This is important for link building tracking.)
Another Panda Update September 2011 – Google issued another Panda update at the end of September. Early reports indicate that it penalized sites that had shown improvements since the last update and continues to favor big brands. Google has had no comment.
Google Places Pictures October 2011 – Google is starting to send out photographers to get interior shots of some businesses like restaurants and salons. Always a good idea to have more photos for your potential customers to see. This is also in Google’s best interest to do since this will offer even more content for searchers and make Google yet another place for searchers to go to get what they want.
YouTube Expansion October 2011 Google payed $100 million to various content producers to create 100 branded YouTube Channels.
Ad Choices November 2011 Google is allowing those with Google accounts to control (to some degree) what kind of ads they want to see.
Fresher Results November 2011 Google will serve up the newest results for specific, time sensitive queries like sports, stocks and news.
Maps Results November 2011 Places results (Maps) have been moved to the right sidebar, affecting what things are shown in the actual search column.
Google+ Growth January 2012 Google+ has 90 million users.
Minor Panda Updates February 2012 It is being reported that a number of small Panda adjustments were made during February 2012, all of which add up to better search results for the user.
Facebook Timeline March 2012 Facebook institutes the Timeline across all accounts. They also predict they will have a billion users by August 2012 and Google + will have an impressive 800 million users.
Google Link Crackdown March 2012 Google has stepped up their detection of linking schemes (aka Blog Networks.) Linked sites are being punished – it’s better to delete all those paid links than to leave them lying around.
Google Search Plus Your World March 2012 Google is adding Google+ pages and your friend’s activities into your Google search screens. More Google properties will likely be folded into the search screens, as well.
Google Adds Rich Snippet Support Globally April 2012 Google has added global rich snippet support, so this will affect what information is shown on search results.
Google Panda Penguin Update April 2012 Google attacked webspam content, links. The best current solution is to have interesting content updated regularly in multiple formats and don’t rely on a single traffic source.
Google Email Translation May 2012 Google emails will automatically be translated for you.