The mobilecore theme is the theme that gets loaded by default when someone visits your site from a mobile browser like the iPhone's Safari browser. This theme is optional, and if you do not have a mobilecore theme, the core theme will be the default theme.

The quickest way to create a mobilecore theme is to copy the core theme folder and rename the folder to "mobilecore". The file structure of the mobilecore theme is identical to the file structure of the core theme. You will need to modify the markup in the index.php file and the styles in your CSS files to make your mobilecore theme a mobile-friendly theme.