Balthisar Tidy is a free application for cleaning, organizing, troubleshooting, and fixing HTML files from a wide variety of sources.
With virtually all of the features of the command line tool and all of the text encodings that Mac OS X offers, Balthisar Tidy will be helping you post better code in no time!
This Cocoa implementation of Dave Raggett`s HTML TIDY is a free utility for doing all of this.
It also works great on the atrociously hard to read markup generated by specialized HTML editors and conversion tools, and can help you identify where you need to pay further attention on making your pages more accessible to people with disabilities.