/*  GRID OF TWO   ============================================================================= */
/* Default mobile size */
  .span_2_of_2 {
    width: 100%; 
  }
  .span_1_of_2 {
    width: 100%; 
  }

@media only screen and (min-width:40em) {   /* 40em will be 40x16 i.e. >= 640px */
/*** Desktop and Large Desktop ***/
  .span_2_of_2 {
    width: 100%; 
  }
  .span_1_of_2 {
    width: 49.2%; 
  }
}