Smartsite 7.3 - ...

Code Mirror is a versatile text editor implemented in Javascript which works in every browser. It features syntax highlighting, (tag) autocompletion, bracket and tag matching, etcetera.

Using the Ctrl-Space key combination, it even features a list of autocompletion hints for e.g. html attributes, dependent on the language (html, css, javascript).
Pressing F11 will toggle the editor into full screen mode.

CodeMirror example