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.[49] 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.[50]
Page and Brin's theory is that the most important pages on the Internet are the pages with the most links leading to them. PageRank thinks of links as votes, where a page linking to another page is casting a vote. The idea comes from academia, where citation counts are used to find the importance of researchers and research. The more often a particular paper is cited by other papers, the more important that paper is deemed. 
The PageRank algorithm outputs a probability distribution used to represent the likelihood that a person randomly clicking on links will arrive at any particular page. PageRank can be calculated for collections of documents of any size. It is assumed in several research papers that the distribution is evenly divided among all documents in the collection at the beginning of the computational process. The PageRank computations require several passes, called "iterations", through the collection to adjust approximate PageRank values to more closely reflect the theoretical true value.
With offline marketing, it's very difficult to tell how people are interacting with your brand before they have an interaction with a salesperson or make a purchase. With digital marketing, you can identify trends and patterns in people's behavior before they've reached the final stage in their buyer's journey, meaning you can make more informed decisions about how to attract them to your website right at the top of the marketing funnel.
Enhanced content such as images, videos, and product lists is another key part of SEO and can also help businesses rank higher on the SERP. Search engines are wary of local listings that are not rich with details about a business and favor results that are reliable, accurate, and consistent, and oftentimes this includes listings that include a lot of enhanced content.
With the advent of portable devices, smartphones, and wearable devices, watches and various sensors, these provide ever more contextual dimensions for consumer and advertiser to refine and maximize relevancy using such additional factors that may be gleaned like: a person's relative health, wealth, and various other status, time of day, personal habits, mobility, location, weather, and nearby services and opportunities, whether urban or suburban, like events, food, recreation, and business. Social context and crowd sourcing influences can also be pertinent factors.
Positioning of a webpage on Google SERPs for a keyword depends on relevance and reputation, also known as authority and popularity. PageRank is Google’s indication of its assessment of the reputation of a webpage: It is non-keyword specific. Google uses a combination of webpage and website authority to determine the overall authority of a webpage competing for a keyword.[34] The PageRank of the HomePage of a website is the best indication Google offers for website authority.[35]
In 2005, in a pilot study in Pakistan, Structural Deep Democracy, SD2[59][60] was used for leadership selection in a sustainable agriculture group called Contact Youth. SD2 uses PageRank for the processing of the transitive proxy votes, with the additional constraints of mandating at least two initial proxies per voter, and all voters are proxy candidates. More complex variants can be built on top of SD2, such as adding specialist proxies and direct votes for specific issues, but SD2 as the underlying umbrella system, mandates that generalist proxies should always be used.
Another disadvantage is that even an individual or small group of people can harm image of an established brand. For instance Dopplegnager is a term that is used to disapprove an image about a certain brand that is spread by anti-brand activists, bloggers, and opinion leaders. The word Doppelganger is a combination of two German words Doppel (double) and Ganger (walker), thus it means double walker or as in English it is said alter ego. Generally brand creates images for itself to emotionally appeal to their customers. However some would disagree with this image and make alterations to this image and present in funny or cynical way, hence distorting the brand image, hence creating a Doppelganger image, blog or content (Rindfleisch, 2016).
Product Listings: If you sell a catalog of products, search engines like Google and Bing offer a specific ad type called product listing ads or PLA’s. These ads highlight your products, including a product image, and have become far more prominent in search results over the past year or two. These ads can do wonders to attract potential customers who are looking for what you’re selling.

Keyword analysis. From nomination, further identify a targeted list of key­words and phrases. Review competitive lists and other pertinent industry sources. Use your preliminary list to determine an indicative number of recent search engine queries and how many websites are competing for each key­word. Prioritize keywords and phrases, plurals, singulars and misspellings. (If search users commonly misspell a keyword, you should identify and use it). Please note that Google will try to correct the term when searching, so use this with care.
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]