Themes are a powerful addition to the ASP.NET framework. By
taking advantage of themes, we can dramatically reduce the amount of content
that we need to add to individual ASP.NET pages. Themes enable us to define the
appearance of a control once and apply the appearance throughout a Web
application. Therefore, themes enable us to easily create Web sites that have a
consistent and maintainable design. This improves the maintainability of our
site and avoids unnecessary duplication of code for shared styles.