There are many reasons explaining why advertisers choose the SEM strategy. First, creating a SEM account is easy and can build traffic quickly based on the degree of competition. The shopper who uses the search engine to find information tends to trust and focus on the links showed in the results pages. However, a large number of online sellers do not buy search engine optimization to obtain higher ranking lists of search results, but prefer paid links. A growing number of online publishers are allowing search engines such as Google to crawl content on their pages and place relevant ads on it. From an online seller's point of view, this is an extension of the payment settlement and an additional incentive to invest in paid advertising projects. Therefore, it is virtually impossible for advertisers with limited budgets to maintain the highest rankings in the increasingly competitive search market.
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.
Optimizing a website may involve editing its content, adding content, modifying HTML, and associated coding to both increase its relevance to specific keywords and to remove barriers to the indexing activities of search engines. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search.