This is EditArea, a free java-script editor for source code.
This editor is designed to edit souce code files in a textarea. The main goal is to allow text formatting, search and replace and syntax highlight (for not too hard text).

This editor is free and freeware distributable (released under LGPL, Apche and BSD licenses).
Main features:

* Easy to install and integrate, only one script include and one function call
* Tabulation support
* Customizable real-time syntax highlighting (currently: PHP, CSS, Javascript, Python, HTML, XML, VB, C, CPP, SQL, Pascal, Basic and probably more...)
* Word-wrap support
* Search and replace (with regexp)
* Auto-indenting new lines
* Line numeration
* Multilanguage support (currently: Croatian, Czech, Danish, Dutch, English, Esperanto, French, German, Italian, Japanese, Macedonian, Polish, Portuguese, Russian, Slovak, Spanish, and probably more...)
* Possible PHP gzip compression (compress the 12 core files to one file of ~30Ko)
* Allow multiple instances
* Full screen mode
* Possible plugin integration
* Possible save and load callback functions
* Possible dynamic content management
* This can work in the same environment than "prototype" and "mootools"'s like libraries.

Link to the official website: http://www.cdolivet.com/index.php?page=editArea