Themes are used to define visual styles for web pages. Themes are made up of a set of elements: skins, Cascading Style Sheets (CSS), images, and other resources. Themes can be applied at the application, page, or server control level. We can create theme by adding App_Themes folder in our project in solution explorer panel. The simple steps are Right click on project and select Add ASP.NET folder – Theme. We can add files into it also. The sample code snippets in this article have been written in C#.