TLibTidy is a Pascal wrapper for the library version of the HTML Tidy program by Dave Ragget.
It's different from Jeffrey Pohlmeyer's wrapper in that all functions are loaded dynamically - because a tidylib.dll file is not required until an instance of the TLibTidy object is actually created, your application can also work without it.
The functions of the library are separated into several modules. Each module has it's own unit containing all the functions and types of that module. You can either low-level-access those directly or use the provided wrapper component (TLibTidy).
Have a look at the demo project for more information on how to use the package. Reading the HTML Tidy documentation may also be helpful.
While I have only tested this with Delphi 7, it should work with previous versions as well. It is not compatible with Kylix or FreePascal, though making the necessary changes should not be too much work.