function changeCategory()
{
  if (document.getElementById)
  {
    var category = document.getElementById('category');
    var classify = document.getElementById('classification');
    classify.disabled = true;

    if (category.options)
    {
      var i = 0;
      for (i = 0; i < category.options.length; ++i)
      {
        if (category.options[i].selected)
        {
          if ((category.options[i].value == "sc") ||
              (category.options[i].value == "sr"))
          {
            classify.disabled = false;
          }
        }
      }
      if (classify.disabled)
        classify.options[0].selected = true;
    }
  }
}


window.onload = changeCategory;