HTML Purifier has documentation for all types of people. Here is an index of all of them.
End-user documentation that contains articles, tutorials and useful information for casual developers using HTML Purifier.
Developer documentation detailing code issues, roadmaps and project conventions.
Proposed features, as well as the associated rambling to get a clear objective in place before attempted implementation.
Miscellaneous essays, research pieces and other reference type material that may not directly discuss HTML Purifier.