
This function improves the given source HTML text, by invoking a
custom version of HTML Tidy utility.
To learn more about Tidy see http://www.w3.org/People/Raggett/tidy/ .
Some particular combinations of errors in source HTML may cause Tidy to
misinterpret the source so the output may be incomplete or corrupted.
This is an  unavoidable problem, due to heruistic nature of the procedure.
 On the other hand, Tidy will process almost any HTML suitable for some
"popular" browser, e.g. Internet Explorer or Netscape Navigator.
