function changeStyle(s) {
  el = document.getElementById("stylesheet");
  if (el) {
  	el.href = "stylesheets/"+s;
  }
}

function adjustStyleToSize() {
  if (window.innerWidth) {
    width = window.innerWidth;
  } else {
    width = document.body.clientWidth;
  }

  if (width > 1250) changeStyle("main1280.css");
  else if (width > 1000) changeStyle("main1024.css");
  else changeStyle("main.css");
}

window.onresize = adjustStyleToSize;
adjustStyleToSize();