Jeff Barczewski is talking about MasterView, a template engine for Rails. MasterView is a Ruby gem that enables the creation of Ruby/Rails views in standards-compliant XHTML. The problem with Rails views, at least in Jeff's view, is that you can't use standard HTML WYSIWYG editing tools to create and modify them. MasterView is a Ruby template language, meaning that you can use it without Rails.
The views produced by MasterView are considerably more sophisticated that those produced by standard Rails. The XHTML compliance is achieved by embedding the template directives in XHTML-compliant attributes in <div/> tags. Jeff demonstrates using Mozilla Composer to edit the HTML forms and other pages. Very nice for building the view. Editing the repeated layout on one page, changes it on all of them.
An admin screen for MasterView allows you to control how pages are rendered, see the status of files rebuild the files, and so on. Tidy is built-in to clean up bad HTML.
Trying to remember which files are where can be frustrating. Moreover, if you have a team where designers were separated from developers, this architecture would probably yield a more natural workflow.