It is a form of Internet marketing that involves the promotion of websites by increasing their visibility in search engine results pages (SERPs) through optimization (both on-page and off-page) as well as through advertising (paid placements, contextual advertising, and paid inclusions). Depending on the context, SEM can be an umbrella term for various means of marketing a website including search engine optimization (SEO), which adjusts or rewrites website content to achieve a higher ranking in search engine results pages, or it may contrast with SEO, focusing on only paid components.
There are three categories of methods and metrics used to optimize websites through search engine marketing.
It involves three "steps:" ensuring the site can be indexed in the search engines, finding the most relevant and popular keywords for the site and its products, and using those keywords on the site in a way that will generate and convert traffic.
How much presence a website has on search engines, can be analyzed through the number of pages of the site that are indexed on search engines (saturation) and how many backlinks the site has (popularity). It requires your pages containing those keywords people are looking for and ensure that they rank high enough in search engine rankings. Most search engines include some form of link popularity in their ranking algorithms.
The followings are major tools measuring various aspects of saturation and link popularity: Link Popularity, Top 10 Google Analysis, and Marketleap's Link Popularity and Search Engine Saturation.
Validators check the invisible parts of websites, highlighting potential problems and many usability issues ensure your website meets W3C code standards. Try to use more than one HTML validator or spider simulator because each tests, highlights, and reports on slightly different aspects of your website.