var elSel = document.getElementById('');
  var i;
  for (i = elSel.length - 1; i>=0; i--) {
    elSel.remove(i);
  }
  
  
var elOptNew = document.createElement('option');
var elSel = document.getElementById('');
elOptNew.text = '[Select A Size]';
elOptNew.value = 0;
try {
  elSel.add(elOptNew, null); // standards compliant; doesn't work in IE
}
catch(ex) {
  elSel.add(elOptNew); // IE only
}