diff --git a/library/HTMLPurifier/AttrTransform/BdoDir.php b/library/HTMLPurifier/AttrTransform/BdoDir.php
index 3993616d..442eface 100644
--- a/library/HTMLPurifier/AttrTransform/BdoDir.php
+++ b/library/HTMLPurifier/AttrTransform/BdoDir.php
@@ -11,6 +11,9 @@ HTMLPurifier_ConfigDef::define(
     'attribute in HTML, or ltr if that is not specified.'
 );
 
+/**
+ * Post-trasnform that ensures that bdo tags have the dir attribute set.
+ */
 class HTMLPurifier_AttrTransform_BdoDir extends HTMLPurifier_AttrTransform
 {
     
diff --git a/library/HTMLPurifier/AttrTransform/ImgRequired.php b/library/HTMLPurifier/AttrTransform/ImgRequired.php
index 5c47c084..f43ddef7 100644
--- a/library/HTMLPurifier/AttrTransform/ImgRequired.php
+++ b/library/HTMLPurifier/AttrTransform/ImgRequired.php
@@ -19,6 +19,9 @@ HTMLPurifier_ConfigDef::define(
     'image is valid but there was no alt attribute present.'
 );
 
+/**
+ * Post-transform that ensures the required attrs of img (alt and src) are set
+ */
 class HTMLPurifier_AttrTransform_ImgRequired extends HTMLPurifier_AttrTransform
 {
     
diff --git a/library/HTMLPurifier/AttrTransform/Lang.php b/library/HTMLPurifier/AttrTransform/Lang.php
index 62297ab3..384b7a7f 100644
--- a/library/HTMLPurifier/AttrTransform/Lang.php
+++ b/library/HTMLPurifier/AttrTransform/Lang.php
@@ -2,9 +2,11 @@
 
 require_once 'HTMLPurifier/AttrTransform.php';
 
-// this transformation may be done pre or post validation, but post is
-// preferred, since invalid languages then will have been dropped.
-
+/**
+ * Post-transform that copies lang's value to xml:lang (and vice-versa)
+ * @note Theoretically speaking, this could be a pre-transform, but putting
+ *       post is more efficient.
+ */
 class HTMLPurifier_AttrTransform_Lang extends HTMLPurifier_AttrTransform
 {
     
diff --git a/library/HTMLPurifier/AttrTransform/TextAlign.php b/library/HTMLPurifier/AttrTransform/TextAlign.php
index 331132de..5e04c627 100644
--- a/library/HTMLPurifier/AttrTransform/TextAlign.php
+++ b/library/HTMLPurifier/AttrTransform/TextAlign.php
@@ -2,6 +2,9 @@
 
 require_once 'HTMLPurifier/AttrTransform.php';
 
+/**
+ * Pre-transform that changes deprecated align attribute to text-align.
+ */
 class HTMLPurifier_AttrTransform_TextAlign
     extends HTMLPurifier_AttrTransform {