Semantic Grid

semantic-grid.scss

header { @include outerRow();
  aside { @include column(4); }
  section { @include column(8); 
    article { @include innerRow();
      header { @include column(2);
               mid-width: 0; }
      div { @include column(10); }
    }
  }
}

div { @include columns(10); }

should be

div { @include column(10); }

remove trailing 's' in 'columns'

I've never seen the mid-width property before, and would like to read up on it. Does anyone know where it is documented? Is it proprietary to SCSS; I couldn't find it in Mozilla MDN's CSS3 documentation.

Why would the outer container be a header element? Seems like the whole page is in there, which means it should be body or something else just inside body.