FLUX 4 is the older version, please see Flux V.
Flux is an advanced HTML5 Web design application, capable of creating stunning sites from scratch. Flux isnt a template based solution, its a creative design environment.
Version 4 introduces FreeCode, a new feature that allows you to completely control your HTML and CSS code, but still retain WYSIWYG capability.
Flux 4 embraces OSX Lion by providing Full Screen Support with an embedded Inspector and Site Manager.
