The quickest way to understand child themes is by example. In this section, you create a simple child theme that modifies the style of the parent theme.
Currently, the default WordPress theme is Twenty Ten. Figure 5-1 shows how the Twenty Ten theme appears on a sample site.
You likely have Twenty Ten on your WordPress site, and Twenty Ten is child theme'ready; therefore, it's a great candidate for creating an example child theme. To keep the names simple, we call the new child theme TwentyTen Child (original, we know).
Like regular themes, a child theme needs to reside in a directory inside the /wp-content/themes directory. The first step to creating a child theme is to add the directory that will hold it. For this example, create a new directory called twentyten-child inside the /wp-content/themes directory.
To register the twentyten-child directory as a theme and ...