Exadel Tiggr: Web Preview feature [in pictures]
Starting with screen prototype, notice that we have two screens (list of invoices and invoice):

Now you would like to preview how this will look in web browser. From menu select Web Preview/Open:

Tiggr will generate HTML/JS/CSS and show you the result in a new browser window:

The orange arrow at the top allows you to switch between different screens:

List of invoices preview in a web browser:

Very nice, I look forward to seeing it grow. First thought is whether or not there will be any form of import / export. The basic functionality that is there looks great.
You can import today by selecting Screen > Save as Image. You can also import/export the screen XML by selecting Project > Clipboard Import/Export. Are you looking for import/export in other formats?