function __isValidString__(name) {
  // test that string does not contains invalid characters
  return (name.search(re_invalidStringChars) < 0);
}
@method DOMImplementation._isValidString - Return true, if string does not contain any illegal chars
 All of the characters 0 through 31 and character 127 are nonprinting control characters.
 With the exception of characters 09, 10, and 13, (Ox09, Ox0A, and Ox0D)
 Note: different from _isValidName in that ValidStrings may contain spaces
@author Jon van Noort (jon@webarcana.com.au)
@param  name : string - the candidate string
@return : boolean