A free program for Android, by appfour.

AIDE is an interactive coding environment for developing websites with HTML/CSS/JavaScript directly on your Android device. AIDE provides an interactive learning experience that allows you to become an expert web developer. It has an integrated development environment (IDE) that includes:

Interactive Coding Lessons – Learn how to code in an interactive environment with step-by-step instructions and interactive lessons.

AIDE with an interactive coding console – AIDE that allows you to run your own code in the console and test your websites.

AIDE with a Filebrowser – A file browser that allows you to access files on your device and the web.

Editor with code completion, error-checking, and refactoring – An editor that provides code completion, real-time error checking, and refactoring.