Separation of style and content

Separation of style and content is a methodology of web design in which the HTML or XHTML contains the page content and information about the structure of the document, but does not define its visual layout (style). The style information is instead contained in an external CSS file.

This is different from traditional web design methodology, in which the markup contains the content and also defines the visual appearance.

Separation of style and content has many benefits, but has only become practical in recent years due to improvements in popular web browsers' CSS implementations.