Try the XML version of this page. If you have problems with it, consult the compatibility page.
These pages are about XML schemas - meta-language for describing the structure of XML documents and validating them. Naturally, there are all sorts of other pages around that cover schemas for XML. Jeni's Schema Pages are dedicated to helping people understand and make the most of using schema languages.
These slides are from the XML Schema tutorial that I gave at Extreme Markup Languages in 2002 and yes, I'm afraid that they were created using PowerPoint. You can download everything, or just the exercises, as zips:
Or browse through the HTML (IE only):
Validating document structures
Building complex type hierarchies
Embedding Schematron in XML Schema
/schema/index.xml by Jeni Tennison; generated using SAXON 6.5.2 from Michael Kay