function cols() {
 var l = document.getElementById('leftcol').offsetHeight;
 var r = document.getElementById('rightcol').offsetHeight;
 if (r >= l) {
  document.getElementById('leftcol').style.height = r-115+ "px";
 } else {
  document.getElementById('rightcol').style.height = l-100+ "px";
 }
}
window.onload = cols;