Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Separation of presentation and content (or "separate content from presentation") is a common idiom, a design philosophy, and a methodology applied in the context of various publishing technology disciplines, including information retrieval, template processing, web design, web development, word processing, desktop publishing, and model-driven development. It is a specific instance of the more general philosophy, separation of concerns.When invoked as an idiom, the underlying concept is to make a distinction between the actual meaning of a document, and how this meaning is presented to its readers. A common example is the em element in HTML, to denote emphasis. Which is part of the content of the document, its presentation may be printing it in an oblique rendering. However since emphasis in a text that is already oblique should in fact be printed normal again or in boldface, and since other texts can also be oblique. Separation of content and presentation marks all those things differently, even though they can be presented in the same way, or marks them identical, and presents them differently.