Visualforce pages that are modular, composed of a number of smaller, reusable building blocks, improve usability by providing consistent appearance and behavior. They are also easier to develop and maintain. Common functionality is defined once in a single place rather than repeated in multiple pages.
Visualforce provides several features you can use to create modular, highly maintainable pages:
Static resources—Reusable images, scripts, stylesheets, and other static content can be stored in static resources, available for embedding in all Visualforce pages in the Force.com organization.
Inclusion—The contents of one Visualforce ...