What is Maqetta?
Maqetta is an open source project that provides WYSIWYG visual authoring of HTML5 user interfaces. The Maqetta application itself is authored in HTML, and therefore runs in the browser without requiring additional plugins or downloads.
Hosted app has been stopped in January 2014. It can be self-hosted downloading last version of the project, 10.0.2, released in May 2013, from Github.