At our April meeting, we finished up from last month comparing how pages validate under different document type declarations. Using both a simple page and one with advanced HTML5 technologies, we saw that while Firefox rendered the pages the same with any doctype, the validation results were completely different.
For more on document types, check the Wikipedia article on the subject.
We then considered the fact that development of XHTML2 has been discontinued. XHTML has some strict requirements for validation, as outlined at this site, and at a future meeting, we will consider the advantages of that strict markup and whether the looser markup rules of HTML5 might be something to be cautious about.
We finished up by looking at XML to get an idea of where the web might have been going before HTML5. We will have some more to say on that topic in May before we move on to considering best practices for going forward with HTML5.