Other Hill Gui Development Framework (abbreviation OHUI as following), embedding Gecko 22.0, is a cross platform, open source GUI Framework. Developers can code html on ff22.0,then load it with OHUI.support xul, html(5),css(3),js, support js vs c++ call each other, size 13MB.OHUI is open source, but not free. about the limition of html5 and css3, you can refer firefox22.0.
https://github.com/yaolixing/OHUI/blob/master/README.md

OHUI v1.9.1