Cascading Style Sheets (CSS)
Templates comprised of HTML code which define a uniform appearance of Web pages on a site.
With an external CSS, a separate page of code controls the layout, fonts, colors, and navigation of all the Web pages. When a change is made on the CSS, such as a font style, that change takes effect on all pages.
With internal CSS, controlling code is embedded among other HTML code for a given Web page. This is useful when changes are needed for a complex Web page and for speeding loading by reusing graphical elements.
Modern Web design takes good advantage of CSS.