Erik Behrends wrote this article about the web and Symphony container. The tooling is much better in Notes 8.5.1 but this article shows how to use the containers at a pretty low level.
Composite applications are an integral part of Lotus Notes since release 8.0. They enable users to assemble loosely coupled components based on Eclipse or NSF views to an application that meets specific business purposes. This powerful technology has been extended with the generic application container framework in Lotus Notes 8.5, which introduces several container components, such as the Generic Browser, Symphony Spreadsheet, Notes View, and Notes PIM containers. Instead of being limited to a single, special-purpose task as regular components are, the container components can be configured in various ways to be used for more complex applications. For example, the Generic Browser container can be used to extract data from specific Web sites or to fill in HTML forms using data provided by other components.