Google Web Designer
Let us handle the HTML5 and CSS3 so you’re free to focus on what you love to do: creating gorgeous visual experiences. A full design suite lets you easily bring any vision to life.
If you’re feeling more hands-on, all the code behind your designs is hand-editable, so you’re never locked out of your own work. Your ideas are now amplified by code – not restricted by it.
Homepage : http://www.google.com/webdesigner/
Tutorial : https://support.google.com/webdesigner/?hl=en