In search engine optimization, the term markup includes the possibility of adding additional information for search engines to data in the source code. Markups in standardized markup languages are used to structure the source code and make it easier for search engines to understand how the markups are processed. Content or source code is usually tagged using tags defined in the markup language or markup language. Structured data is important for search engine optimization as it can be used to generate rich snippets.
Markup (in the various markup languages) makes it possible to provide information with additional information, so that presentation, structure, and formatting can be regulated or instructions for further processing can be given to the performing computers. A browser as an application knows how to deal with the source code in HTML and CSS formatting because it can interpret the markup. This requires standards which basically make up the meta-definitions for markup languages. HTML is based on XML, which in turn is based on principles of SGML. A markup is always preceded by the definition of the document type, which determines which symbols or tags can be used. This is described with a syntax. XML is also extensible. You can add your own definitions of elements and types, as well as communication with scripting languages or other elements.
Markup languages can be generally divided into three areas. Descriptive markup languages determine properties of elements and their status within a structure. Procedural markup languages define how a document is created, displayed or processed. PDF or LaTeX are examples of formats. Additionally, there are light markup languages that are used in wikis, forums or blogs. These only contain a limited selection of elements. The formatting and structuring options in Wikipedia serve as an example.
With regard to markup or markup languages, there is always an important rule being focused on. Markup and content should be separated - in other words, the presentation of the content is separate from the actual content. Especially for large websites, formatting is handled through CSS files and the structure for the content is specified in HTML. Markup can also be valid or invalid with regard to the defining metalanguage. Certain rules must be applied with HTML, CSS, and XML, so that the code can be read by a terminal. Whether a particular document is valid in a markup language can be easily checked through the W3C validator.
Markup is very important in the field of search engine optimization. All areas of a web document may contain certain elements which have an impact on the behavior of search engines.
Some markup is also useful for users, for example, a hover text that is visible on a link and tells users where the link leads or a clear structure that was generated by individual HTML tags. The markup should be helpful and shape the user experience. At the same time markup is essential to make your website search-engine-friendly, especially with regard to the preparation of data for crawlers. You can deny or grant access to crawlers to a given document with markup.
With the increasing use of intelligent search assistants, the importance of markup is growing. This is because these assistants can process structured data more easily. For conventional web searches, markup is nowadays indispensable for displaying rating stars, prices or event data in the snippets in the SERPs.