How can I use JTidy to clean a dirty tag which is not a html tag

Hello!
    I  use JTidy to parse HTML file to XHTML file,  but I get a error bug :

    "line 1 column 1 - Error: <o> is not recognized!
      line 1 column 9 - Error: o is not recognized!"

    so I fail to parse.

   now , I hope to clean a dirty tag  , such as '<o>' , which is not a HTML
tag ,
   what can I do?

  Thanks for your help!