An expert system
that knows
about real world HTML!
Popular W3C Open Source utility for fixing up HTML
Tidy corrects the markup in a way that matches where possible the observed rendering in popular browsers
Can convert presentation markup to CSS rules
Knows about ASP and PHP and can be taught about new tags, e.g. Cold Fusion
Does a good job on cleaning up the HTML exported from Microsoft Word'97 and Word'2000
Makes it trivial to roll content over to XHTML
Tidy is available on most platforms and has been integrated into numerous authoring environments