A web
style sheet is a form of
separation of presentation and content for
web design in which the
markup (i.e.,
HTML or
XHTML) of a
webpage contains the page's semantic content and structure, but does not define its visual layout (style). Instead, the style is defined in an external style sheet file using a
style sheet language such as
CSS or
XSLT. This design approach is identified as a "separation" because it largely supersedes the antecedent methodology in which a page's markup defined both style and structure.