While Themes and Skins are new to ASP.NET 2.0, the underlying concepts have been around for a long time. For those unfamiliar with Themes and Skins, skins give web designers greater flexibility to manipulating ASP.NET server side controls (calendars, datagrids, etc…) through Styles / Cascading Style Sheets (CSS). Themes logically group the design tier of an application into a common folder or directory (a Theme folder(s)), giving developers the ability to programmatically change (swap), or expose these Themes to the user.

Learn more: ASP.NET Themes and Skins Overview.
See a live example here: ASP.NET 2.0 Colorful Web Site Starter Kit.

The concept of interchanging layout and changing design styles (Themes) has been around for quite some time. The W3C Recommendation for Style Sheets in HTML documents outlines the “alternate stylesheet” that should be interchanged through the browsers menu; unfortunately Internet Explorer (IE) fails to support this method.

An example: changing style sheets with a Mozilla based browser (Firefox).

See the live example (if you’re not using IE) at: www.damowmow.com.

Other methods for changing design layouts (Themes) range from Client Side Scripts (JavaScript) to Server Side Scripts (ASP, PHP, ASP.NET, and so on).

Learn more about style interchanging scripts and more here: Style Switching - css-discuss.

Themes and Skins are a welcome addition to ASP.NET 2.0, they offer a simple solution for grouping design specific files, and a nice way to programmatically change these Themes. However; this simplistic approach significantly hampers the power of Cascading Style Sheets – I’ll discuss my difficulties / problems in subsequent posts.