How can a Theme be applied to a web application ?

Answer:

There are 3 levels at which a theme can be applied for a web application.
They are discussed as below:
1. At the page level - In this level, you have to use the Theme or StyleSheetTheme attribute of the @ Page directive.

2. At the application level - In this level, a theme can be applied to all pages in an application by setting the <pages> element in the application configuration file.

3. At the web server level - In this level, you have to define the <pages> element in machine.config file. This will apply the theme to all the web applications on that web server.