function checkForScroll () {
  var mainDiv = document.getElementById("main");
  var pageHeight = mainDiv.offsetHeight;
  var windowHeight = window.innerHeight;
  var left = document.getElementById('leftborder');
  var right = document.getElementById('rightborder');
  if (pageHeight >= windowHeight) { // scroll
    mainDiv.style.paddingBottom = "10px";
  } else { // no scroll
    mainDiv.style.height = "100%";
  }
  left.style.height = mainDiv.offsetHeight;
  right.style.height = mainDiv.offsetHeight;
}