When you render a web you are normally expected to take care of the styling by using separately referenced CSS files. For example, you might import a theme style sheet for the framework that you are using.
In the updated UI framework, each widget can optionally define its own CSS resources, including the ability to specify different resources for different media types. If that widget is used on a page then Surf will automatically include those CSS resources within a single aggregated CSS resource loaded on the page. The same principle is applied to localization files so the use of a widget ensures that its National Language Support (NLS) properties automatically built into a JavaScript resource loaded on the page. Widgets can scope their message bundles to ensure that there are no collisions and the core message handling function is smart enough to work through all of the message scopes in a widgets ancestry to ensure that the most specific message is displayed.