Today, it's less common for the look and feel of an application to be a static, unchanging aspect. Instead, they ship with a handful of themes the user can choose from. Or, the support to easily create themes is built into the software. This allows our customers to decide how our software should look for their users. In addition to packaged themes that update the look and feel of our application, individual style preferences may be set.
If we want our application to have the ability to change themes upon request, we have to put a lot of design and architecture into our CSS and the markup that uses it. While this topic goes way beyond the scope of this book, it's worth looking at the tools available for assisting in generating themes.
The first tool at our disposal in this area is a CSS framework. Like JavaScript frameworks, CSS frameworks define consistent patterns and conventions. It's then up to us, the component authors, to figure out how to apply these...