Note that this was known as HTML5 Boilerplate, which was an OK name but now that I have a use-case for this code that name is no longer suitable.
So what the hell is this then?
1 - It's HTML5.
2 - It's media queries.
3 - It's a fluid grid.
So the basic plan here is to prototype an adaptive design that changes in response to the viewport. This is experimental code - the grid is a pretty simple 24 column fluid grid, float left bizzo with a last-col class - the stuff that is not worked on very much is how to make the grid respond to the viewport via media queries - we know in theory how to do this, but just how far I can push this in a generic Drupal theme is what this is all about. I am using this to prototype ideas for changes to Bartik in D8 where we want to bring in some level of responsiveness.
The initial media queries implementation is based on Andy Clarkes Responsive Boilerplate: http://www.stuffandnonsense.co.uk/blog/about/hardboiled_css3_media_queries/
It will work fine as a starter theme for a responsive design.
IE6/7/8 are support by way of the HTML5shiv which the theme pulls from Google code.