ASP.NET FAQ : Themes vs. Cascading Style Sheets
A theme is a collection of property settings that allow you to define the
look of pages and controls, and then apply the look consistently across pages in
a Web application, across an entire Web application, or across all Web
applications on a server.
Cascading Style Sheets (CSS) is a stylesheet language used to describe the
presentation of a document written in a markup language(i.e HTML).
Themes are similar to cascading style sheets in that both themes and style
sheets define a set of common attributes that can be applied to any page.
However, themes differ from style sheets in the following ways:.
- Themes are control-based, not HTML-based. Themes can define many properties
of a control or page, not just style properties. For example, using themes, you
can specify the graphics for a TreeView control, the template layout of a
GridView control, and so on.
- Themes do not cascade the way style sheets do. For example, by default,
property values override local property values unless you explicitly apply the
theme as a style sheet theme.
- Only one theme can be applied to each page. You cannot apply multiple themes
to a page, unlike style sheets where multiple style sheets can be applied.
- Themes are applied on the server where as stylesheet on the client side.
- Themes can be applied through configuration files.