HTML to XHTML conversion / correction class

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Hello Everyone,
I am looking for a good reliable class that will check for valid XHTML
tags based on Transitional or Strict Doctypes for example.

Have you got any idea or are you aware of any class that will do the
Job ?

Thank you,
I am awaiting for your answers.

Site Timeline