function delCusTopic(obj) {
  // Deletes only if total number of topics are greater than 1, else shows
  // error message.
  if (checkCount > 1) {
    var value;

    // Extract custom topic value.
    value = obj.parentNode.querySelector('.cusTopicsClass textarea').value;

    // Removes custom topic element from UI.
    $('custom_topics').removeChild(obj.parentNode);

    // Removes custom topic element either from temporary array(if topic is
    // not yet saved) or from saved topic list and saves new list to
    // local storage.
    var flag = 0;
    for (var i = 0; i < tempCusTopics.length; i++) {
      if (tempCusTopics[i] == value) {
        tempCusTopics.splice(i, 1);
        flag = 1;
        break;
      }
    }

    if (flag == 0) {
      var keywords = JSON.parse(window.localStorage.getItem('keywords'));
      for (i = 0; i < keywords.length; i++) {
        if (keywords[i] == value) {
          keywords.splice(i, 1);
          break;
        }
      }
      if (keywords.length > 0) {
        window.localStorage.setItem('keywords', JSON.stringify(keywords));
      } else {
        window.localStorage.removeItem('keywords');
      }
    }

    checkCount--;
    $('submit_button').disabled = false;
  } else {
    showUserMessages('save_status', 2.5, 'noTopic');
  }
  $('newKeyword').readOnly = false;
}
Delete custom topic whenever users click on delete icon.
@param {HTMLTableColElement} obj HTML table column element to be deleted.