“Dangling links are simply links that point to any page with no outgoing links. They affect the model because it is not clear where their weight should be distributed, and there are a large number of them. Often these dangling links are simply pages that we have not downloaded yet……….Because dangling links do not affect the ranking of any other page directly, we simply remove them from the system until all the PageRanks are calculated. After all the PageRanks are calculated they can be added back in without affecting things significantly.”
Google uses a hyperlink based algorithm (known as ‘PageRank’) to calculate the popularity and authority of a page, and while Google is far more sophisticated today, this is still a fundamental signal in ranking. SEO can therefore also include activity to help improve the number and quality of ‘inbound links’ to a website, from other websites. This activity has historically been known as ‘link building’, but is really just marketing a brand with an emphasis online, through content or digital PR for example.
SEO is not an appropriate strategy for every website, and other Internet marketing strategies can be more effective like paid advertising through pay per click (PPC) campaigns, depending on the site operator's goals. Search engine marketing (SEM), is 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 PageRank 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 now shows 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 analysed 2.5 million websites and 51.3% of the pages were loaded by a mobile device . Google has been one of the companies that have utilised 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.
Search engine optimization (SEO) is the process of affecting the online visibility of a website or a web page in a web search engine's unpaid results—often referred to as "natural", "organic", or "earned" results. In general, the earlier (or higher ranked on the search results page), and more frequently a website appears in the search results list, the more visitors it will receive from the search engine's users; these visitors can then be converted into customers. SEO may target different kinds of search, including image search, video search, academic search, news search, and industry-specific vertical search engines. 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.