Programming Microsoft ASP.NET 2.0 Core Reference

A master page contains regions that each derived page can customize.

A derived page, known as a content page, is a collection of markup blocks that the runtime will use to fill the regions in the master page.

Content pages can't contain information other than contents for the master's placeholders.

Regions in the master page can have default content that can be used if the content page doesn't provide any.

You can define various masters for a page and have the system automatically pick up a particular one based on the browser's user agent string.

Master pages can be nested and expose a strong-typed object model.

Themes are a collection of settings spread over various files that the ASP.NET runtime uses to give the whole site (or page) a consistent user interface.

Themes become a kind of attribute, and they can be exported from one application to the next and applied to pages on the fly.

Themes differ from CSS files because they let you style ASP.NET control properties and not just HTML elements.

A theme contains skin files, CSS files, and images, plus any other auxiliary file you might find useful.

A skin file is a collection of ASP.NET control declarations. The system ensures that after instantiation each control of that type in the page will have exactly the same set of attributes.

The wizard control manages multiple views inside a single control and provides an auto-generated user interface for you to move back and forth between views as you do in a desktop wizard.