htmlpurifier/WYSIWYG

WYSIWYG - What You See Is What You Get
    HTMLPurifier: A Pretty Good Fit for TinyMCE and FCKeditor

Javascript-based WYSIWYG editors, simply stated, are quite amazing.  But I've
always been wary about using them due to security issues: they handle the
client-side magic, but once you've been served a piping hot load of unfiltered
HTML, what should be done then?  In some situations, you can serve it uncleaned,
since you only offer these facilities to trusted(?) authors.

Unfortunantely, for blog comments and anonymous input, BBCode, Textile and
other markup languages still reign supreme.  Put simply: filtering HTML is
hard work, and these WYSIWYG authors don't offer anything to alleviate that
trouble.  Therein lies the solution:

HTMLPurifier is perfect for filtering pure-HTML input from WYSIWYG editors.

Enough said.