Klipse
Klipse is a JavaScript plugin for embedding interactive code snippets
... Clojurescript lib. The Klipse plugin can be easily styled with CSS, which can be applied both to the Klipse plugin's own elements, and to the CodeMirror editor's elements. Much of the styling you'll apply will be to CodeMirror, as it contains all the CSS classes to style the code itself. Surrounding CodeMirror is the Klipse plugin, the styles of which control the plugin's borders, and the executed code's output.