Index: htmlpurifier/HTMLPurifier_DefinitionCache_Drupal.php
===================================================================
--- htmlpurifier/HTMLPurifier_DefinitionCache_Drupal.php	(revision 34)
+++ htmlpurifier/HTMLPurifier_DefinitionCache_Drupal.php	(working copy)
@@ -93,3 +93,21 @@
   
 }
 
+class HTMLPurifier_Filter_MyIframe extends HTMLPurifier_Filter
+{
+    public $name = 'MyIframe';
+
+    public function preFilter($html, $config, $context) {
+        return preg_replace("/iframe/", "img class=\"MyIframe\" ", preg_replace("/<\/iframe>/", "", $html));
+    }
+
+    public function postFilter($html, $config, $context) {
+       $post_regex = '#<img class="MyIframe" ([^>]+)>#';
+       return preg_replace_callback($post_regex, array($this, 'postFilterCallback'), $html);
+    }
+
+    protected function postFilterCallback($matches) {
+        return '<iframe '.$matches[1].'></iframe>';
+    }
+}
+
Index: htmlpurifier/htmlpurifier.module
===================================================================
--- htmlpurifier/htmlpurifier.module	(revision 34)
+++ htmlpurifier/htmlpurifier.module	(working copy)
@@ -312,6 +312,9 @@
   $config->set('Core.AggressivelyFixLt', TRUE);
   $config->set('Cache.DefinitionImpl', 'Drupal');
   
+  // added for iframe support
+  $config->set('Filter.Custom', array( new HTMLPurifier_Filter_MyIframe() ));
+  
   // Filter HTML doesn't allow external images, so neither will we...
   // for now. This can be configured off.
   $config->set('URI.DisableExternalResources', TRUE);