Apache Pivot is an open-source platform for building rich internet applications in Java. It combines the enhanced productivity and usability features of a modern RIA toolkit with the robustness of the Java platform. Pivot applications are written using a combination of Java and XML and can be run either as an applet or as a standalone, optionally offline, desktop application.
Like other modern development platforms, Pivot provides a comprehensive set of foundation classes that together comprise a "framework". These classes form the building blocks upon which more complex and sophisticated applications can be built.
see here the apache pivot's project page
This document was created by a set of user interface designers, usability specialists, and visual designers, to outline a usable web application look and feel that can be followed consistently throughout a product line. We created it originally for use within Sun Microsystems, to be used for the web applications built here. However, we would like to share these guidelines with anyone else who may benefit from them for creating their own web applications. While some of the guidelines refer to Sun-specific elements and contexts, we are confident that you, the reader, will be able to interpret how they can be reapplied to your applications. We hope you find these guidelines valuable, and wish you success in creating your own powerful and highly usable web applications, building on these usability-tested and carefully designed guidelines.
see here for the full guide