If you are web designer or developer and if you are sell your works on Envato, I think this plugin ideal and very important for you. So, you can show your WordPress themes, Joomla templates or HTML templates with our awesome FBar demo bar plugin. This is a demo bar would be shown on top of page, allow users to preview another theme. The demo bar is customisable at style.css.

Demo: http://codecanyon.net/item/fbar-responsive-php-theme-switcher-demo-bar/5045579