Simple, SASS based, grid system

_grid.sass

!columns        ||= 12
!column_width   ||= 60
!column_margin  ||= 20

.row
  overflow: hidden
  margin: 0 auto
  width: #{!columns * !column_width + !columns * !column_margin}px

  .row
    margin: 0 -#{!column_margin / 2}px
    display: inline-block
    width: auto

@for !i from 1 through !columns
  .column_#{!i}
    float: left
    overflow: hidden
    display: inline
    margin: 0 #{!column_margin / 2}px
    width: #{!column_width * !i + !column_margin * (!i - 1)}px

screen.sass

!columns        = 12
!column_width   = 60
!column_margin  = 20

@import grid.sass