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.[22] 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.
Sometimes, Google turns up the dial on demands on ‘quality’, and if your site falls short, a website traffic crunch is assured. Some sites invite problems ignoring Google’s ‘rules’ and some sites inadvertently introduce technical problems to their site after the date of a major algorithm update and are then impacted negatively by later refreshes of the algorithm.

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.[18][19] 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.[20] 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.

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."[68][69]
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.[54] Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's search engine results page.[55]
Most people search on mobile devices - You don't need statistics to show you that in the past few years the online mobile market has exploded, overtaking desktops years ago. Optimizing websites for mobile browsers is critical if you want to rank well in search engine results pages. If you’re unsure how your website measures up, enter your site’s URL in Google's Mobile-Friendly Test.
Everything for Google these days comes down to “Customer Experience”. Page speeds, table of content, the relevancy of content, length of content, uniqueness of content, jump links, video in the content, relevant headers, less broken links, customized 404 pages etc are all indicative of improving customer experience on th website and hence helps you rank better.
QUOTE: “Google Webmaster Tools notice of detected doorway pages on xxxxxxxx – Dear site owner or webmaster of xxxxxxxx, We’ve detected that some of your site’s pages may be using techniques that are outside Google’s Webmaster Guidelines. Specifically, your site may have what we consider to be doorway pages – groups of “cookie cutter” or low-quality pages. Such pages are often of low value to users and are often optimized for single words or phrases in order to channel users to a single location. We believe that doorway pages typically create a frustrating user experience, and we encourage you to correct or remove any pages that violate our quality guidelines. Once you’ve made these changes, please submit your site for reconsideration in Google’s search results. If you have any questions about how to resolve this issue, please see our Webmaster Help Forum for support.” Google Search Quality Team
Google is all about ‘user experience’ and ‘visitor satisfaction’ in 2019 so it’s worth remembering that usability studies have shown that a good page title length is about seven or eight words long and fewer than 64 total characters. Longer titles are less scan-able in bookmark lists, and might not display correctly in many browsers (and of course probably will be truncated in SERPs).
Keywords are as much about your audience as they are about your content, because you might describe what you offer in a slightly different way than some people ask for it. To create content that ranks well organically and drives visitors to your site, you need to understand the needs of those visitors — the language they use and the type of content they seek. You can do this by talking to your customers, frequenting forums and community groups, and doing your own keyword research with a tool like Keyword Explorer.