Editing Existing CSS Templates and Layouts in NetBeans IDE
By Geertjan on Feb 24, 2013
On this page you can download dozens of free HTML/CSS templates:
Run the application from the IDE into the embedded browser (or into Chrome, with the installed NetBeans/Chrome plugin) and you'll find a wonderful environment for developing the template into a full blown application.
And did I mention all of this is open source? And extensible? And free? Well, in case I didn't, all of the above is open source and extensible and free.