Adding local.xml to your Magento theme

As you have seen, Magento provides fallbacks to fill in the files not provided by your theme to help ensure your website functions as effectively as possible. You can overwrite the layout information in your Magento theme by applying a local.xml file to your Magento theme.

Create a file called local.xml in your theme's /app/design/frontend/default/m18/layout/ directory, and include the following XML:

<?xml version="1.0"?>
<layout>
</layout>

This is the very least your Magento XML layout file requires: all of the subsequent changes to your theme's layout need to be written in the <layout> element.