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]
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.[36] The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to improve their rankings on the search engine.[37] Although Google Penguin has been presented as an algorithm aimed at fighting web spam, it really focuses on spammy links[38] 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 [39]. 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.

In addition to processing the text content on your web pages, Google will also try to figure out what your images are about as well. Alt Text is a short description that you can customize for each image to let Google know what the image is about. Setting short, descriptive Alt Texts through our site builder will help Google better associate your web pages with the search terms you're trying to target.
Google is looking for a “website that is well cared for and maintained” so you need to keep content management systems updated, check for broken image links and HTML links. If you create a frustrating user experience through sloppy website maintenance – expect that to be reflected in some way with a lower quality rating. Google Panda October 2014 went for e-commerce pages that were optimised ‘the old way’ and are now classed as ‘thin content’.
Other research shows that exact-match domains that are deemed to be relevant, valuable, and high-quality can see a ranking boost because of it. However, if you already have an established website, you don’t need to go looking for an exact-match domain for your business; focus on a URL that reflects your business and optimize the heck out of it instead!
In short, nobody is going to advise you to create a poor UX, on purpose, in light of Google’s algorithms and human quality raters who are showing an obvious interest in this stuff. Google is rating mobile sites on what it classes is frustrating UX – although on certain levels what Google classes as ‘UX’ might be quite far apart from what a UX professional is familiar with in the same ways as Google’s mobile rating tools differ from, for instance,  W3c Mobile testing tools.
QUOTE:  Each piece of duplication in your on-page SEO strategy is ***at best*** wasted opportunity. Worse yet, if you are aggressive with aligning your on page heading, your page title, and your internal + external link anchor text the page becomes more likely to get filtered out of the search results (which is quite common in some aggressive spaces). Aaron Wall, 2009
Naturally, business owners want to rank for lots of keywords in organic listings with their website. The challenge for webmasters and SEO is that Google doesn’t want business owners to rank for lots of keywords using autogenerated content especially when that produces A LOT of pages on a website using (for instance) a list of keyword variations page-to-page.
QUOTE: “Duplicated content is often not manipulative and is commonplace on many websites and often free from malicious intent. Copied content can often be penalised algorithmically or manually. Duplicate content is not penalised, but this is often not an optimal set-up for pages, either. Be VERY careful ‘spinning’ ‘copied’ text to make it unique!” Shaun Anderson, Hobo, 2018

There used to be a time where you could add a lot of keywords to your pages and posts, do some old-fashioned keyword stuffing, and you’d rank in search engines. But a text with a lot of the same keywords in it is not a pleasant read. And because users find this kind of copy terrible to read, Google finds it terrible too. That’s why ranking in Google by doing keyword stuffing, fortunately, became hard to do.

Ranking refers to the process search engines use to determine where a particular piece of content should appear on a SERP. Search visibility refers to how prominently a piece of content is displayed in search engine results. Highly visible content (usually the content that ranks highest) may appear right at the top of organic search results or even in a featured snippet, while less-visible content may not appear until searchers click to page two and beyond
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.[40] 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[41] in addition to their URL submission console.[42] Yahoo! formerly operated a paid submission service that guaranteed crawling for a cost per click;[43] however, this practice was discontinued in 2009.

NOTE, in 2019, the HTML title element you choose for your page, may not be what Google chooses to include in your SERP snippet. The search snippet title and description is very much QUERY & DEVICE dependant these days. Google often chooses what it thinks is the most relevant title for your search snippet, and it can use information from your page, or in links to that page, to create a very different SERP snippet title.
Naturally, business owners want to rank for lots of keywords in organic listings with their website. The challenge for webmasters and SEO is that Google doesn’t want business owners to rank for lots of keywords using autogenerated content especially when that produces A LOT of pages on a website using (for instance) a list of keyword variations page-to-page.

Search engines use complex mathematical algorithms to interpret which websites a user seeks. In this diagram, if each bubble represents a website, programs sometimes called spiders examine which sites link to which other sites, with arrows representing these links. Websites getting more inbound links, or stronger links, are presumed to be more important and what the user is searching for. In this example, since website B is the recipient of numerous inbound links, it ranks more highly in a web search. And the links "carry through", such that website C, even though it only has one inbound link, has an inbound link from a highly popular site (B) while site E does not. Note: Percentages are rounded.
QUOTE: “So there’s three things that you really want to do well if you want to be the world’s best search engine you want to crawl the web comprehensively and deeply you want to index those pages and then you want to rank or serve those pages and return the most relevant ones first….. we basically take PageRank as the primary determinant and the more PageRank you have that is the more people who link to you and the more reputable those people are the more likely it is we’re going to discover your page…. we use page rank as well as over 200 other factors in our rankings to try to say okay maybe this document is really authoritative it has a lot of reputation because it has a lot of PageRank … and that’s kind of the secret sauce trying to figure out a way to combine those 200 different ranking signals in order to find the most relevant document.” Matt Cutts, Google
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.

QUOTE: “Starting April 21 (2015), we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high-quality search results that are optimized for their devices”. GOOGLE
For example, within the HubSpot Blogging App, users will find as-you-type SEO suggestions. This helpful inclusion serves as a checklist for content creators of all skill levels. HubSpot customers also have access to the Page Performance App, Sources Report, and the Keyword App. The HubSpot Marketing Platform will provide you with the tools you need to research keywords, monitor their performance, track organic search growth, and diagnose pages that may not be fully optimized.