This is the easiest way to add custom css and/or javascript to your site. Two large windows with css and javascript syntax highlighting makes it super easy to read and write code. JK Development console also uses AJAX to save the css and javascript data – meaning that the page won’t reload and you can keep on working without have to look for that last spot you edited.
Hope you like it! 🙂
Syntax highlightning by ACE (http://ace.c9.io/).
This plugin is available for download for your site.