In version 2.1, HTML Purifier's URI validation and filtering handling
system has been revamped with a new, extensible URIFilter system. Also
notable features include preservation of emoticons in PHP5 with
%Core.AggressivelyFixLt, standalone and lite download versions,
transforming relative URIs to absolute URIs, Ruby in XHTML 1.1, a Phorum
mod, and UTF-8 font names.  Notable bug-fixes include refinement of
the auto-paragraphing algorithm (no longer experimental), better XHTML
1.1 support and the removal of the contents of <style> elements.