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.
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.[13] 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.[14]
While backlinks are still an important factor used by search engines to determine content quality, linkless mentions are given more weight than ever before. This is partially due to the perception is that linkless mentions are more genuine, unlike black hat SEO techniques like paid links. Social media mentions are also playing an increasingly important role in evaluating website quality.
Site. Migration. No two words elicit more fear, joy, or excitement to a digital marketer. When the idea was shared three years ago, the company was excited. They dreamed of new features and efficiency. But as SEOs we knew better. We knew there would be midnight strategy sessions with IT. More UAT environments than we could track. Deadlines, requirements, and compromises forged through hallway chats. ... The result was a stable transition with minimal dips in traffic. What we didn't know, however, was the amount of cross-functional coordination that was required to pull it off. Learn more in this video!
Many websites rely on other traffic generation methods such as traffic from social media, email, referrals, and direct traffic sources over search engines. For sites like these, SEO errors aren’t as important because search engines aren’t their #1 traffic source. For a smaller website, a couple of errors can have a much bigger negative effect than those same errors on a larger website.
This relationship between rankings and clicks (and traffic) is strongest amongst the top 3 search results. However, changing layout of the search results pages is constantly changing, with the inclusion of Google’s Knowledge Graph data and the integration of Universal Search elements (SERP Features) like videos, maps and Google Shopping ads. These developments can mean that the top 3 organic rankings are no longer the 3 best positions on the SERP. This has been demonstrated in heatmap and eye-tracking tests.

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.
Since heading tags typically make text contained in them larger than normal text on the page, this is a visual cue to users that this text is important and could help them understand something about the type of content underneath the heading text. Multiple heading sizes used in order create a hierarchical structure for your content, making it easier for users to navigate through your document.
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.[15] Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban.[16] Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.[17]