//= require modernizr // last-child pseudo selector // github.com/Modernizr/Modernizr/pull/304

Modernizr.addTest('lastchild', function(){

return Modernizr.testStyles("#modernizr div {width:100px} #modernizr :last-child{width:200px;display:block}", function (elem) {
  return elem.lastChild.offsetWidth > elem.firstChild.offsetWidth;
}, 2);

});