[Context: HL Kit Basic Concepts and Terminology Visual Building Blocks]
The Kit makes is easy to manage and tailor the visual look and behavior of the data files through the use of styles. Every portal must specify a variety of colors, fonts, bitmaps, borders, and other facets to be used when displaying that portal. In order to achieve a consistent interface, you'll typically want to use the same basic look and behaviors for most portals of the same type. Similarly, if you want to change the visual look or behaviors of a particular portal type, you'll want to do it for all of them.
To keep things convenient and easy, you'll define styles that encapsulate the common visual behaviors for each portal type. Each portal is then assigned a style that dictates its visual behavior. Changing the behavior for a portal requires simply changing the assigned style, while changing the behavior of all portals of a type requires simply changing the style definition itself.