WebKit is a powerful, multi-platform HTML engine used in open source and commercial/proprietary products alike. WebKitGTK+ is the port of WebKit built on GTK+ and integrated into the GNOME developer platform. WebKitGTK+ is developed upstream as part of the main WebKit project, so it's always up to date with the latest HTML5 features.
WebKitGTK+ makes it easy to add web functionality to your application, or to use HTML5 and associated technologies to create dynamic user interfaces quickly.
WebKitGTK+ demo tutorial
WebKitGTK+ Reference Manual
The WebKitGTK+ web site