Web-Based Code Editor By Adobe – Brackets
The editor focuses on simplicity and, rather than too many panels, the quick-edit UI is the main thing.
A "live development" feature syncs a browser with the editor and displays any changes instantly.
It is integrated with the Chrome's Developer Tools and JSLint for debugging.
Brackets, although being web-based, works in a native shell (Win & Mac versions available) to reach the filesystem.