function isID(strString) {
    var strValidChars = ".-@0123456789_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    var strChar;
    var blnResult = true;
    
    for (i = 0; i < strString.length && blnResult == true; i++) {
      strChar = strString.charAt(i);
      if (strValidChars.indexOf(strChar) == -1) {
        blnResult = false;
      }
    }
    return blnResult;
  }