This is a pure html+CSS Javascript prettifier. HTML markup is very rich in classnames, and for each AST node an HTML element is created and structure is preserved in a straightforward way.
All the CSS style that give the prettify stuff like espaces, indenting and colors is available at the right and is editable by the user, just edit it and press the button "do it".
For more information go to the style_prettify1 indentator implementation sources.
Please paste your JavaScript code in the first text area and press "do it".
You can edit this style that will apply to prettify generated markup.