2008 March, Jim Cheshire, “Using Web Page Views”, in Using Microsoft Expression Web 2, special edition, Indianapolis, Ind.: Que Publishing, Pearson Education, ↑ISBN, page 138:
If you uncheck either of these check boxes, [Microsoft] Expression Web 2 will create all new Web pages with uppercase tag names and/or attributes. Current Web standards require that HTML tag names and attributes be lowercase. Therefore, pages created with either of these boxes unchecked will not be compatible with existing standards.