How to Create a Theme Development Environment for a Live WordPress Site
With the help of an excellent plugin for WordPress called Theme Switcher, this tutorial will allow you to easily switch between the live site and development versions using two different themes on the same installation of WordPress. We’ll do this by creating a bar at the top of the page which will clearly show you if you’re viewing the live theme (what everyone else sees) or the development theme with a link to switch between the two.

