TODO List

1.3 release
 - Make URI validation routines tighter (especially mailto)
 - More extensive URI filtering schemes (see docs/proposal-new-directives.txt)
 - Allow for background-image and list-style-image (see above)
 - Error logging for filtering/cleanup procedures
 - Rich set* methods and config file loaders for HTMLPurifier_Config

1.4 release
 - Add various "levels" of cleaning
    - Related: Allow strict (X)HTML
 - More fine-grained control over escaping behavior
    - Silently drop content inbetween SCRIPT tags (can be generalized to allow
      specification of elements that, when detected as foreign, trigger removal
      of children, although unbalanced tags could wreck havoc (or at least
      delete the rest of the document)).

1.5 release
 - Additional support for poorly written HTML
    - Implement all non-essential attribute transforms
    - Microsoft Word HTML cleaning (i.e. MsoNormal)

2.0 release
 - Formatters for plaintext
    - Auto-paragraphing (be sure to leverage fact that we know when things
      shouldn't be paragraphed, such as lists and tables).
    - Linkify URLs
    - Smileys
    - Linkification for HTML Purifier docs: notably configuration and
      class names

3.0 release
 - Extended HTML capabilities based on namespacing and tag transforms
    - Hooks for adding custom processors to custom namespaced tags and
      attributes, offer default implementation
    - Lots of documentation and samples

Ongoing
 - Lots of profiling, make it faster!
 - Plugins for major CMSes (very tricky issue)

Unknown release (on a scratch-an-itch basis)
 - Fixes for Firefox's inability to handle COL alignment props (Bug 915)
 - Automatically add non-breaking spaces to empty table cells when
   empty-cells:show is applied to have compatibility with Internet Explorer
 - Convert RTL/LTR override characters to <bdo> tags, or vice versa on demand.
   Also, enable disabling of directionality
 - Append something to duplicate IDs so they're still usable (impl. note: the
   dupe detector would also need to detect the suffix as well)
 - Have 'lang' attribute be checked against official lists

Encoding workarounds
 - Non-lossy dumb alternate character encoding transformations, achieved by
   numerically encoding all non-ASCII characters
 - Semi-lossy dumb alternate character encoding transformations, achieved by
   encoding all characters that have string entity equivalents

Requested
 - Native content compression, whitespace stripping (don't rely on Tidy, make
   sure we don't remove from <pre> or related tags)
 - Win32 Phalanger C# binaries (?)
 - Remove redundant tags, ex. <u><u>Underlined</u></u>. Implementation notes:
    1. Analyzing which tags to remove duplicants
    2. Ensure attributes are merged into the parent tag
    3. Extend the tag exclusion system to specify whether or not the
    contents should be dropped or not (currently, there's code that could do
    something like this if it didn't drop the inner text too.)

Wontfix
 - Non-lossy smart alternate character encoding transformations (unless
   patch provided)
 - Pretty-printing HTML, users can use Tidy on the output on entire page