Mark Shust shows how to use Magento's XSD files as documentation for valid layout XML tags and attributes. The blank theme's headblocks.xml demonstrates page configuration, including CSS tags in the HTML head and meta tags for format detection.
If we take a look at the default headblocks layout XML file from the blank theme we will see an example of a page configuration in Magento. This includes the CSS tags that are added to the page along with a format detection meta tag. The default head blocks layout XML file is just a standard layout XML file that adds tags to the HTML head of all pages. You can add page configuration to just about any XML file, though it doesn't need to be in default head blocks. If we command click into the page configuration XSD file we will see a list of all of the XML tags that we can use in this file and if we command click into this head XSD file we will see a self documenting API of sorts of all of the tags available to us. Some of these, such as link type are groups of attributes that can then be assigned to multiple other types, and this head type defines all of the tags we can use in the head. We can use these XSD tags so we don't need to constantly wonder what tags are available to us.
