.Drag and drop graphical user interface
.Live preview - you don't have to save or export
.Bootstrap 3 design
.Developing catalogue of recent pre-made blocks
.Different publishing methods - local drive, host, FTP
.Various service providers - Google Drive, Amazon S3, Github
The main options show that Mobirise free bootstrap builder is quite simple to use. The minimalistic interface allows real-time preview web site for various screen formats. This doesn't have a script editing console as well as WYSIWYG.
Mobirise is very optimized for mobile guests, letting clients generate 100 % responsive, and mobile friendly web-sites. It's made with Bootstrap 3 which is a highly effective mobile platform. Which means you could also work with any bootstrap themes.
For more information on the latest release or to download the Website Builder visit: http://mobirise.com/