This extension contains a new datatype to store HTML code in an class attribute. The datatype is extending the eztext datatype. There are two differences:

The output (view.tpl) is not escaped (no wash() operator)
The input (edit.tpl) uses the javascript library codemirror

"CodeMirror is a versatile text editor implemented in JavaScript for the browser. It is specialized for editing code, and comes with a number of language modes and addons that implement more advanced editing functionality."

Currently, the extension only allows to edit HTML, CSS and Javascript code.