Search engine optimization (SEO) is the process of increasing the quality and quantity of website traffic by increasing the visibility of a website or a web page to users of a web search engine.
SEO refers to the improvement of unpaid results (known as “natural” or “organic” results) and excludes direct traffic/visitors and the purchase of paid placement.
SEO may target different kinds of searches, including image search, video search, academic search, news search, and industry-specific vertical search engines.
Optimizing a website may involve editing its content, adding content, and modifying HTML and associated coding to both increase its relevance to specific keywords and remove barriers to the indexing activities of search engines like Google, Yahoo etc. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search.
As an Internet marketing strategy, SEO considers how search engines work, the computer-programmed algorithms that dictate search engine behavior, what people search for, the actual search terms or keywords typed into search engines, and which search engines are preferred by their targeted audience. SEO is performed because a website will receive more visitors from a search engine the higher the website ranks in the search engine results page (SERP). These visitors can then be converted into customers.
SEO differs from local search engine optimization in that the latter is focused on optimizing a business’ online presence so that its web pages will be displayed by search engines when a user enters a local search for its products or services. The former instead is more focused on national or international searches.
Webmasters and content providers began optimizing websites for search engines in the mid-1990s, as the first search engines were cataloging the early Web. Initially, all webmasters only needed to submit the address of a page, or URL, to the various engines which would send a “spider” to “crawl” that page, extract links to other pages from it, and return information found on the page to be indexed. The process involves a search engine spider downloading a page and storing it on the search engine’s own server. A second program, known as an indexer, extracts information about the page, such as the words it contains, where they are located, and any weight for specific words, as well as all links the page contains. All of this information is then placed into a scheduler for crawling at a later date.
Website owners recognized the value of a high ranking and visibility in search engine results, creating an opportunity for both white hat and black hat SEO practitioners. According to industry analyst Danny Sullivan, the phrase “search engine optimization” probably came into use in 1997. Sullivan credits Bruce Clay as one of the first people to popularize the term. On May 2, 2007, Jason Gambert attempted to trademark the term SEO by convincing the Trademark Office in Arizona that SEO is a “process” involving manipulation of keywords and not a “marketing service.”
Early versions of search algorithms relied on webmaster-provided information such as the keyword meta tag or index files in engines like ALIWEB. Meta tags provide a guide to each page’s content. Using metadata to index pages was found to be less than reliable, however, because the webmaster’s choice of keywords in the meta tag could potentially be an inaccurate representation of the site’s actual content. Inaccurate, incomplete, and inconsistent data in meta tags could and did cause pages to rank for irrelevant searches.[dubious ] Web content providers also manipulated some attributes within the HTML source of a page in an attempt to rank well in search engines. By 1997, search engine designers recognized that webmasters were making efforts to rank well in their search engine, and that some webmasters were even manipulating their rankings in search results by stuffing pages with excessive or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.
By relying so much on factors such as keyword density which were exclusively within a webmaster’s control, early search engines suffered from abuse and ranking manipulation. To provide better results to their users, search engines had to adapt to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed with numerous keywords by unscrupulous webmasters. This meant moving away from heavy reliance on term density to a more holistic process for scoring semantic signals. Since the success and popularity of a search engine is determined by its ability to produce the most relevant results to any given search, poor quality or irrelevant search results could lead users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate. In 2005, an annual conference, AIRWeb (Adversarial Information Retrieval on the Web), was created to bring together practitioners and researchers concerned with search engine optimization and related topics.
Companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients.Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban. Google’s Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.
Some search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide information and guidelines to help with website optimization. Google has a Sitemaps program to help webmasters learn if Google is having any problems indexing their website and also provides data on Google traffic to the website.Bing Webmaster Tools provides a way for webmasters to submit a sitemap and web feeds, allows users to determine the “crawl rate”, and track the web pages index status.
In 2015, it was reported that Google was developing and promoting mobile search as a key feature within future products. In response, many brands began to take a different approach to their Internet marketing strategies.
Relationship with Google
In 1998, two graduate students at Stanford University, Larry Page and Sergey Brin, developed “Backrub”, a search engine that relied on a mathematical algorithm to rate the prominence of web pages. The number calculated by the algorithm, PageRank, is a function of the quantity and strength of inbound links. PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfs the web, and follows links from one page to another. In effect, this means that some links are stronger than others, as a higher PageRank page is more likely to be reached by the random web surfer.
Page and Brin founded Google in 1998. Google attracted a loyal following among the growing number of Internet users, who liked its simple design. Off-page factors (such as PageRank and hyperlink analysis) were considered as well as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the kind of manipulation seen in search engines that only considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link building tools and schemes to influence the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focused on exchanging, buying, and selling links, often on a massive scale. Some of these schemes, or link farms, involved the creation of thousands of sites for the sole purpose of link spamming.
By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to reduce the impact of link manipulation. In June 2007, The New York Times’ Saul Hansell stated Google ranks sites using more than 200 different signals. The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions. Patents related to search engines can provide information to better understand search engines. In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users.
In December 2009, Google announced it would be using the web search history of all its users in order to populate search results. On June 8, 2010 a new web indexing system called Google Caffeine was announced. Designed to allow users to find news results, forum posts and other content much sooner after publishing than before, Google caffeine was a change to the way Google updated its index in order to make things show up quicker on Google than before. According to Carrie Grimes, the software engineer who announced Caffeine for Google, “Caffeine provides 50 percent fresher results for web searches than our last index…”Google Instant, real-time-search, was introduced in late 2010 in an attempt to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to increase search rankings. With the growth in popularity of social media sites and blogs the leading engines made changes to their algorithms to allow fresh content to rank quickly within the search results.
In February 2011, Google announced the Panda update, which penalizes websites containing content duplicated from other websites and sources. Historically websites have copied content from one another and benefited in search engine rankings by engaging in this practice. However, Google implemented a new system which punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to improve their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at fighting web spam, it really focuses on spammy links by gauging the quality of the sites the links are coming from. The 2013 Google Hummingbird update featured an algorithm change designed to improve Google’s natural language processing and semantic understanding of web pages. Hummingbird’s language processing system falls under the newly recognized term of ‘Conversational Search’ where the system pays more attention to each word in the query in order to better match the pages to the meaning of the query rather than a few words . With regards to the changes made to search engine optimization, for content publishers and writers, Hummingbird is intended to resolve issues by getting rid of irrelevant content and spam, allowing Google to produce high-quality content and rely on them to be ‘trusted’ authors.
The leading search engines, such as Google, Bing and Yahoo!, use crawlers to find pages for their algorithmic search results. Pages that are linked from other search engine indexed pages do not need to be submitted because they are found automatically. The Yahoo! Directory and DMOZ, two major directories which closed in 2014 and 2017 respectively, both required manual submission and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for free to ensure that all pages are found, especially pages that are not discoverable by automatically following links in addition to their URL submission console. Yahoo! formerly operated a paid submission service that guaranteed crawling for a cost per click; however, this practice was discontinued in 2009.
Search engine crawlers may look at a number of different factors when crawling a site. Not every page is indexed by the search engines. The distance of pages from the root directory of a site may also be a factor in whether or not pages get crawled.
Today, most people are searching on Google using a mobile device. In November 2016, Google announced a major change to the way crawling websites and started to make their index mobile-first, which means the mobile version of your website becomes the starting point for what Google includes in their index. In May 2019, Google updated the rendering engine of their crawler to be the latest version of Chromium (74 at the time of the announcement). Google indicated that they would regularly update the Chromium (web browser) rendering engine to the latest version.  In December of 2019, Google began updating the User-Agent string of their crawler to reflect the latest Chrome version used by their rendering service. The delay was to allow webmasters time to update their code that responded to particular bot User-Agent strings. Google ran evaluations and felt confident the impact would be minor. 
To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl certain files or directories through the standard robots.txt file in the root directory of the domain. Additionally, a page can be explicitly excluded from a search engine’s database by using a meta tag specific to robots (usually <meta name=”robots” content=”noindex”> ). When a search engine visits a site, the robots.txt located in the root directory is the first file crawled. The robots.txt file is then parsed and will instruct the robot as to which pages are not to be crawled. As a search engine crawler may keep a cached copy of this file, it may on occasion crawl pages a webmaster does not wish crawled. Pages typically prevented from being crawled include login specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam.
A variety of methods can increase the prominence of a webpage within the search results. Cross linking between pages of the same website to provide more links to important pages may improve its visibility.
Writing content that includes frequently searched keyword phrase, so as to be relevant to a wide variety of search queries will tend to increase traffic. Updating content so as to keep search engines crawling back frequently can give additional weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to improve the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via multiple URLs, using the canonical link element or via 301 redirects can help make sure links to different versions of the URL all count towards the page’s link popularity score.
White hat versus black hat techniques
SEO techniques can be classified into two broad categories: techniques that search engine companies recommend as part of good design (“white hat”), and those techniques of which search engines do not approve (“black hat”). The search engines attempt to minimize the effect of the latter, among them spamdexing. Industry commentators have classified these methods, and the practitioners who employ them, as either white hat SEO, or black hat SEO. White hats tend to produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently once the search engines discover what they are doing.
An SEO technique is considered white hat if it conforms to the search engines’ guidelines and involves no deception. As the search engine guidelines are not written as a series of rules or commandments, this is an important distinction to note. White hat SEO is not just about following guidelines but is about ensuring that the content a search engine indexes and subsequently ranks is the same content a user will see. White hat advice is generally summed up as creating content for users, not for search engines, and then making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its intended purpose. White hat SEO is in many ways similar to web development that promotes accessibility, although the two are not identical.
Black hat SEO attempts to improve rankings in ways that are disapproved of by the search engines, or involve deception. One black hat technique uses hidden text, either as text colored similar to the background, in an invisible div, or positioned off screen. Another method gives a different page depending on whether the page is being requested by a human visitor or a search engine, a technique known as cloaking. Another category sometimes used is grey hat SEO. This is in between black hat and white hat approaches, where the methods employed avoid the site being penalized but do not act in producing the best content for users. Grey hat SEO is entirely focused on improving search engine rankings.
Search engines may penalize sites they discover using black or grey hat methods, either by reducing their rankings or eliminating their listings from their databases altogether. Such penalties can be applied either automatically by the search engines’ algorithms, or by a manual site review. One example was the February 2006 Google removal of both BMW Germany and Ricoh Germany for use of deceptive practices. Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google’s search engine results page.
As marketing strategy
SEO is not an appropriate strategy for every website, and other Internet marketing strategies can be more effective, such as paid advertising through pay per click (PPC) campaigns, depending on the site operator’s goals. Search engine marketing (SEM) is the practice of designing, running and optimizing search engine ad campaigns. Its difference from SEO is most simply depicted as the difference between paid and unpaid priority ranking in search results. Its purpose regards prominence more so than relevance; website developers should regard SEM with the utmost importance with consideration to visibility as most navigate to the primary listings of their search. A successful Internet marketing campaign may also depend upon building high quality web pages to engage and persuade, setting up analytics programs to enable site owners to measure results, and improving a site’s conversion rate. In November 2015, Google released a full 160 page version of its Search Quality Rating Guidelines to the public, which revealed a shift in their focus towards “usefulness” and mobile search. In recent years the mobile market has exploded, overtaking the use of desktops, as shown in by StatCounter in October 2016 where they analyzed 2.5 million websites and found that 51.3% of the pages were loaded by a mobile device . Google has been one of the companies that are utilizing the popularity of mobile usage by encouraging websites to use their Google Search Console, the Mobile-Friendly Test, which allows companies to measure up their website to the search engine results and how user-friendly it is.
SEO may generate an adequate return on investment. However, search engines are not paid for organic search traffic, their algorithms change, and there are no guarantees of continued referrals. Due to this lack of guarantees and certainty, a business that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors. Search engines can change their algorithms, impacting a website’s placement, possibly resulting in a serious loss of traffic. According to Google’s CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day. It is considered a wise business practice for website operators to liberate themselves from dependence on search engine traffic. In addition to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.
Optimization techniques are highly tuned to the dominant search engines in the target market.
The search engines’ market shares vary from market to market, as does competition.
In 2003, Danny Sullivan stated that Google represented about 75% of all searches. In markets outside the United States, Google’s share is often larger, and Google remains the dominant search engine worldwide as of 2007. As of 2006, Google had an 85–90% market share in Germany. While there were hundreds of SEO firms in the US at that time, there were only about five in Germany. As of June 2008, the market share of Google in the UK was close to 90% according to Hitwise. That market share is achieved in a number of countries.
As of 2009, there are only a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a given market, it is lagging behind a local player. The most notable example markets are China, Japan, South Korea, Russia and the Czech Republic where respectively Baidu, Yahoo! Japan, Naver, Yandex and Seznam are market leaders.
Successful search optimization for international markets may require professional translation of web pages, registration of a domain name with a top level domain in the target market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are essentially the same, regardless of language.
On October 17, 2002, SearchKing filed suit in the United States District Court, Western District of Oklahoma, against the search engine Google. SearchKing’s claim was that Google’s tactics to prevent spamdexing constituted a tortious interference with contractual relations. On May 27, 2003, the court granted Google’s motion to dismiss the complaint because SearchKing “failed to state a claim upon which relief may be granted.”
In March 2006, KinderStart filed a lawsuit against Google over search engine rankings. KinderStart’s website was removed from Google’s index prior to the lawsuit, and the amount of traffic to the site dropped by 70%. On March 16, 2007, the United States District Court for the Northern District of California (San Jose Division) dismissed KinderStart’s complaint without leave to amend, and partially granted Google’s motion for Rule 11 sanctions against KinderStart’s attorney, requiring him to pay part of Google’s legal expenses.
- “SEO – search engine optimization”. Webopedia.
- Beel, Jöran and Gipp, Bela and Wilde, Erik (2010). “Academic Search Engine Optimization (ASEO): Optimizing Scholarly Literature for Google Scholar and Co” (PDF). Journal of Scholarly Publishing. pp. 176–190. Retrieved April 18, 2010.CS1 maint: multiple names: authors list (link)
- “Inside AdWords: Building for the next moment” Google Inside Adwords May 15, 2015.
- Ortiz-Cordova, A. and Jansen, B. J. (2012) Classifying Web Search Queries in Order to Identify High Revenue Generating Customers. Journal of the American Society for Information Sciences and Technology. 63(7), 1426 – 1441.
- Brian Pinkerton. “Finding What People Want: Experiences with the WebCrawler” (PDF). The Second International WWW Conference Chicago, USA, October 17–20, 1994. Retrieved May 7, 2007.
- “Intro to Search Engine Optimization | Search Engine Watch”. searchenginewatch.com. Retrieved June 29, 2017.
- Danny Sullivan (June 14, 2004). “Who Invented the Term “Search Engine Optimization”?”. Search Engine Watch. Archived from the original on April 23, 2010. Retrieved May 14, 2007. See Google groups thread.
- “Trademark/Service Mark Application, Principal Register”. Retrieved May 30, 2014.
- “Trade Name Certification”. State of Arizona.
- Cory Doctorow (August 26, 2001). “Metacrap: Putting the torch to seven straw-men of the meta-utopia”. e-LearningGuru. Archived from the original on April 9, 2007. Retrieved May 8, 2007.
- Pringle, G., Allison, L., and Dowe, D. (April 1998). “What is a tall poppy among web pages?”. Proc. 7th Int. World Wide Web Conference. Retrieved May 8, 2007.CS1 maint: multiple names: authors list (link)
- Laurie J. Flynn (November 11, 1996). “Desperately Seeking Surfers”. New York Times. Retrieved May 9, 2007.
- Jason Demers (January 20, 2016). “Is Keyword Density Still Important for SEO”. Forbes. Retrieved August 15, 2016.
- “AIRWeb”. Adversarial Information Retrieval on the Web, annual conference. Retrieved October 4, 2012.
- David Kesmodel (September 22, 2005). “Sites Get Dropped by Search Engines After Trying to ‘Optimize’ Rankings”. Wall Street Journal. Retrieved July 30, 2008.
- Adam L. Penenberg (September 8, 2005). “Legal Showdown in Search Fracas”. Wired Magazine. Retrieved August 11, 2016.
- Matt Cutts (February 2, 2006). “Confirming a penalty”. mattcutts.com/blog. Retrieved May 9, 2007.
- “Google’s Guidelines on Site Design”. Retrieved April 18, 2007.
- “Bing Webmaster Guidelines”. bing.com. Retrieved September 11, 2014.
- “Sitemaps”. Retrieved May 4, 2012.
- “By the Data: For Consumers, Mobile is the Internet” Google for Entrepreneurs Startup Grind September 20, 2015.
- Brin, Sergey & Page, Larry (1998). “The Anatomy of a Large-Scale Hypertextual Web Search Engine”. Proceedings of the seventh international conference on World Wide Web. pp. 107–117. Retrieved May 8, 2007.
- “Google’s co-founders may not have the name recognition of say, Bill Gates, but give them time: Google hasn’t been around nearly as long as Microsoft”. October 15, 2008.
- Thompson, Bill (December 19, 2003). “Is Google good for you?”. BBC News. Retrieved May 16, 2007.
- Zoltan Gyongyi & Hector Garcia-Molina (2005). “Link Spam Alliances” (PDF). Proceedings of the 31st VLDB Conference, Trondheim, Norway. Retrieved May 9, 2007.
- Hansell, Saul (June 3, 2007). “Google Keeps Tweaking Its Search Engine”. New York Times. Retrieved June 6, 2007.
- Danny Sullivan (September 29, 2005). “Rundown On Search Ranking Factors”. Search Engine Watch. Archived from the original on May 28, 2007. Retrieved May 8, 2007.
- Christine Churchill (November 23, 2005). “Understanding Search Engine Patents”. Search Engine Watch. Archived from the original on February 7, 2007. Retrieved May 8, 2007.
- “Google Personalized Search Leaves Google Labs”. searchenginewatch.com. Search Engine Watch. Archived from the original on January 25, 2009. Retrieved September 5, 2009.
- “8 Things We Learned About Google PageRank”. www.searchenginejournal.com. Retrieved August 17, 2009.
- “PageRank sculpting”. Matt Cutts. Retrieved January 12, 2010.
- “Google Loses “Backwards Compatibility” On Paid Link Blocking & PageRank Sculpting”. searchengineland.com. Retrieved August 17, 2009.
- “Personalized Search for everyone”. Retrieved December 14, 2009.
- “Our new search index: Caffeine”. Google: Official Blog. Retrieved May 10, 2014.
- “Relevance Meets Real-Time Web”. Google Blog.
- “Google Search Quality Updates”. Google Blog.
- “What You Need to Know About Google’s Penguin Update”. Inc.com.
- “Google Penguin looks mostly at your link source, says Google”. Search Engine Land. October 10, 2016. Retrieved April 20, 2017.
- “FAQ: All About The New Google “Hummingbird” Algorithm”. www.searchengineland.com. Retrieved March 17, 2018.
- “Submitting To Directories: Yahoo & The Open Directory”. Search Engine Watch. March 12, 2007. Archived from the original on May 19, 2007. Retrieved May 15, 2007.
- “What is a Sitemap file and why should I have one?”. Retrieved March 19, 2007.
- “Search Console – Crawl URL”. Retrieved December 18, 2015.
- “Submitting To Search Crawlers: Google, Yahoo, Ask & Microsoft’s Live Search”. Search Engine Watch. March 12, 2007. Archived from the original on May 10, 2007. Retrieved May 15, 2007.
- Cho, J., Garcia-Molina, H. (1998). “Efficient crawling through URL ordering”. Proceedings of the seventh conference on World Wide Web, Brisbane, Australia. Retrieved May 9, 2007.CS1 maint: multiple names: authors list (link)
- “Mobile-first Index”. Retrieved March 19, 2018.
- Phan, Doantam (November 4, 2016). “Mobile-first Indexing”. Official Google Webmaster Central Blog. Retrieved January 16, 2019.
- “The new evergreen Googlebot”. Official Google Webmaster Central Blog. Retrieved March 2, 2020.
- “Updating the user agent of Googlebot”. Official Google Webmaster Central Blog. Retrieved March 2, 2020.
- “Newspapers Amok! New York Times Spamming Google? LA Times Hijacking Cars.com?”. Search Engine Land. May 8, 2007. Retrieved May 9, 2007.
- “The Most Important SEO Strategy”. clickz.com. ClickZ. Retrieved April 18, 2010.
- “Bing – Partnering to help solve duplicate content issues – Webmaster Blog – Bing Community”. www.bing.com. Retrieved October 30, 2009.
- Andrew Goodman. “Search Engine Showdown: Black hats vs. White hats at SES”. SearchEngineWatch. Archived from the original on February 22, 2007. Retrieved May 9, 2007.
- Jill Whalen (November 16, 2004). “Black Hat/White Hat Search Engine Optimization”. searchengineguide.com. Retrieved May 9, 2007.
- “What’s an SEO? Does Google recommend working with companies that offer to make my site Google-friendly?”. Retrieved April 18, 2007.
- Andy Hagans (November 8, 2005). “High Accessibility Is Effective Search Engine Optimization”. A List Apart. Retrieved May 9, 2007.
- Matt Cutts (February 4, 2006). “Ramping up on international webspam”. mattcutts.com/blog. Retrieved May 9, 2007.
- Matt Cutts (February 7, 2006). “Recent reinclusions”. mattcutts.com/blog. Retrieved May 9, 2007.
- “Introduction to Search Engine Optimization: Getting Started With SEO to Achieve Business Goals” (PDF).
- Tapan, Panda (2013). “Search Engine Marketing: Does the Knowledge Discovery Process Help Online Retailers?”. IUP Journal of Knowledge Management. 11 (3): 56–66. ProQuest 1430517207.
- Melissa Burdon (March 13, 2007). “The Battle Between Search Engine Optimization and Conversion: Who Wins?”. Grok.com. Archived from the original on March 15, 2008. Retrieved April 10, 2017.
- “Search Quality Evaluator Guidelines” How Search Works November 12, 2015.
- Titcomb, James. “Mobile web usage overtakes desktop for first time”. www.telegraph.co.uk. The Telegraph. Retrieved March 17, 2018.
- Andy Greenberg (April 30, 2007). “Condemned To Google Hell”. Forbes. Archived from the original on May 2, 2007. Retrieved May 9, 2007.
- Matt McGee (September 21, 2011). “Schmidt’s testimony reveals how Google tests algorithm changes”.
- Jakob Nielsen (January 9, 2006). “Search Engines as Leeches on the Web”. useit.com. Retrieved May 14, 2007.
- Graham, Jefferson (August 26, 2003). “The search engine that could”. USA Today. Retrieved May 15, 2007.
- Greg Jarboe (February 22, 2007). “Stats Show Google Dominates the International Search Landscape”. Search Engine Watch. Retrieved May 15, 2007.
- Mike Grehan (April 3, 2006). “Search Engine Optimizing for Europe”. Click. Retrieved May 14, 2007.
- Jack Schofield (June 10, 2008). “Google UK closes in on 90% market share”. Guardian. London. Retrieved June 10, 2008.
- “Search King, Inc. v. Google Technology, Inc., CIV-02-1457-M” (PDF). docstoc.com. May 27, 2003. Retrieved May 23, 2008.
- Stefanie Olsen (May 30, 2003). “Judge dismisses suit against Google”. CNET. Retrieved May 10, 2007.
“Technology & Marketing Law Blog: KinderStart v. Google Dismissed—With Sanctions Against KinderStart’s Counsel”. blog.ericgoldman.org. Retrieved June 23, 2008.
“Technology & Marketing Law Blog: Google Sued Over Rankings—KinderStart.com v. Google”. blog.ericgoldman.org. Retrieved June 23, 2008.