$(window).resize(setDim);

​

function setDim() {

    var windowWidth = $(window).innerWidth()- 3; //the 3 is for the 1px margin between the divs

​

  var windowHeight = $(window).innerHeight() - 70;

​

  $(".one").innerWidth(windowWidth / 3);

  $(".two").innerWidth(windowWidth / 3);

  $(".three").innerWidth(windowWidth / 3);

  $(".one").innerHeight(windowHeight);

  $(".two").innerHeight(windowHeight);

  $(".three").innerHeight(windowHeight);

}

​

setDim();