diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,10 @@
 # Change Log
 
+## 2.1.0
+
+* Fix removal of earliest active format element
+* Fix DOM node attribute matching
+
 ## 2.0.7
 
 * Update benchmarks for ST MonadFail removal
diff --git a/src/Zenacy/HTML/Internal/DOM.hs b/src/Zenacy/HTML/Internal/DOM.hs
--- a/src/Zenacy/HTML/Internal/DOM.hs
+++ b/src/Zenacy/HTML/Internal/DOM.hs
@@ -45,7 +45,9 @@
   , domElementHasAttr
   , domElementFindAttr
   , domElementAttrValue
+  , domAttrEq
   , domAttrMerge
+  , domAttrSet
   , domMatch
   , domLastChild
   , domMapID
@@ -111,6 +113,13 @@
   , insert
   , keys
   )
+import Data.Set
+  ( Set
+  )
+import qualified Data.Set as Set
+  ( empty
+  , insert
+  )
 import Data.Sequence
   ( Seq(..)
   , ViewL(..)
@@ -492,11 +501,20 @@
 domMatch d i j =
   case (domGetNode d i, domGetNode d j) of
     (Just (DOMElement _ _ n1 s1 a1 _), Just (DOMElement _ _ n2 s2 a2 _)) ->
-      n1 == n2 && s1 == s2 && a1 == a1
+      n1 == n2 && s1 == s2 && domAttrEq a1 a2
     (Just (DOMTemplate _ _ s1 a1 _ ), Just (DOMTemplate _ _ s2 a2 _)) ->
-      s1 == s2 && a1 == a1
+      s1 == s2 && domAttrEq a1 a2
     _otherwise ->
       False
+
+-- | Determine if two sequences of attributes are equivalent.
+domAttrEq :: Seq DOMAttr -> Seq DOMAttr -> Bool
+domAttrEq a b = domAttrSet a == domAttrSet b
+
+-- | Converta an attribute sequence to an attribute set in order
+-- to be insensitive to order.
+domAttrSet :: Seq DOMAttr -> Set DOMAttr
+domAttrSet = foldr Set.insert Set.empty
 
 -- | Returns the last child of a node if it exists.
 domLastChild :: DOM -> DOMID -> Maybe DOMID
diff --git a/src/Zenacy/HTML/Internal/Parser.hs b/src/Zenacy/HTML/Internal/Parser.hs
--- a/src/Zenacy/HTML/Internal/Parser.hs
+++ b/src/Zenacy/HTML/Internal/Parser.hs
@@ -883,17 +883,26 @@
 activeFormatAddMarker Parser {..} =
   uref parserActiveFormatList (ParserFormatMarker:)
 
+-- | Limits matching active format elements up to the first
+-- marker to two so that a third can be added (Noah's Ark clause).
+activeFormatLimit :: (DOMID -> Bool) -> [ParserFormatItem] -> [ParserFormatItem]
+activeFormatLimit match xs =
+  f 0 xs
+  where
+    f :: Int -> [ParserFormatItem] -> [ParserFormatItem]
+    f n [] = []
+    f n (e@(ParserFormatMarker):es) = e : es
+    f n (e@(ParserFormatElement domId _):es)
+      | match domId = if n < 2 then e : f (n + 1) es else f n es
+      | otherwise = e : f n es
+
 -- | Adds an element to the list of active format elements.
 activeFormatAddElement :: Parser s -> Token -> DOMID -> ST s ()
 activeFormatAddElement p@Parser {..} t x = do
   d <- getDOM p
   a <- activeFormatList p
-  let match (ParserFormatElement y _) = domMatch d x y
-      b = takeWhile (not . formatItemIsMarker) a
-      n = (foldr (\i z -> z + if match i then 1 else 0) 0 b) :: Int
-      a' = if n < 3 then a else removeFirst match a
-      e' = ParserFormatElement x t : a'
-  wref parserActiveFormatList e'
+  wref parserActiveFormatList $
+    ParserFormatElement x t : activeFormatLimit (domMatch d x) a
 
 -- | Adds the current node to the list of active format elements.
 activeFormatAddCurrentNode :: Parser s -> Token -> ST s ()
@@ -952,15 +961,15 @@
   case a of
     [] -> pure ()
     (x:xs)
-      | isOpen e x -> pure ()
+      | openOrMarker e x -> pure ()
       | otherwise -> do
-          let b = reverse . takeWhile (not . isOpen e) $ a
+          let b = reverse . takeWhile (not . openOrMarker e) $ a
               a' = drop (length b) a
           reopen p b a'
 
 -- | Determines is a format item is open.
-isOpen :: [DOMID] -> ParserFormatItem -> Bool
-isOpen x = \case
+openOrMarker :: [DOMID] -> ParserFormatItem -> Bool
+openOrMarker x = \case
    ParserFormatMarker -> True
    ParserFormatElement i _ -> i `elem` x
 
diff --git a/test/Examples.hs b/test/Examples.hs
new file mode 100644
--- /dev/null
+++ b/test/Examples.hs
@@ -0,0 +1,107 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module Examples
+  ( testExamples
+  ) where
+
+import Test.Framework
+  ( Test
+  , testGroup
+  )
+import Test.Framework.Providers.HUnit
+  ( testCase
+  )
+import Test.HUnit
+  ( assertEqual
+  )
+import Data.Text
+  ( Text
+  )
+import qualified Data.Text as T
+  ( pack
+  )
+import Zenacy.HTML
+
+testExamples :: Test
+testExamples = testGroup "Examples"
+  [ testMisnested
+  , testUnexpected
+  , testUnclosed
+  ]
+
+testMisnested :: Test
+testMisnested = testCase "Misnested tags" $ do
+  flip (assertEqual "13.2.10.1 Misnested tags")
+    (htmlRender $ htmlParseEasy
+    "<html><head></head><body><p>1<b>2<i>3</b>4</i>5</p></body></html>")
+    "<html><head></head><body><p>1<b>2<i>3</i></b><i>4</i>5</p></body></html>"
+  flip (assertEqual "13.2.10.2 Misnested tags")
+    (htmlRender $ htmlParseEasy
+    "<html><head></head><body><b>1<p>2</b>3</p></body></html>")
+    "<html><head></head><body><b>1</b><p><b>2</b>3</p></body></html>"
+
+testUnexpected :: Test
+testUnexpected = testCase "Unexpected markup in tables" $ do
+  flip (assertEqual "13.2.10.3 Unexpected markup in tables")
+    (htmlRender $ htmlParseEasy
+    "<html><head></head><body><table><b><tr><td>aaa</td></tr>bbb</table>ccc</body></html>")
+    "<html><head></head><body>\
+    \<b></b><b>bbb</b><table><tbody><tr><td>aaa</td></tr></tbody></table><b>ccc</b>\
+    \</body></html>"
+
+testUnclosed :: Test
+testUnclosed = testCase "Unclosed formatting elements" $ do
+  flip (assertEqual "13.2.10.6 Unclosed formatting elements")
+    (htmlRender $ htmlParseEasy
+    "<!DOCTYPE html>\
+    \<p><b class=x><b class=x><b><b class=x><b class=x><b>X\
+    \<p>X\
+    \<p><b><b class=x><b>X\
+    \<p></b></b></b></b></b></b>X")
+
+    "<!DOCTYPE html><html><head></head><body>\
+    \<p>\
+      \<b class=\"x\">\
+        \<b class=\"x\">\
+          \<b>\
+            \<b class=\"x\">\
+              \<b class=\"x\">\
+                \<b>X</b>\
+              \</b>\
+            \</b>\
+          \</b>\
+        \</b>\
+      \</b>\
+    \</p>\
+    \<p>\
+      \<b class=\"x\">\
+        \<b>\
+          \<b class=\"x\">\
+            \<b class=\"x\">\
+              \<b>X</b>\
+            \</b>\
+          \</b>\
+        \</b>\
+      \</b>\
+    \</p>\
+    \<p>\
+      \<b class=\"x\">\
+        \<b>\
+          \<b class=\"x\">\
+            \<b class=\"x\">\
+              \<b>\
+                \<b>\
+                  \<b class=\"x\">\
+                    \<b>X</b>\
+                  \</b>\
+                \</b>\
+              \</b>\
+            \</b>\
+          \</b>\
+        \</b>\
+      \</b>\
+    \</p>\
+    \<p>X</p>\
+    \</body></html>"
diff --git a/test/Issues.hs b/test/Issues.hs
new file mode 100644
--- /dev/null
+++ b/test/Issues.hs
@@ -0,0 +1,41 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module Issues
+  ( testIssues
+  ) where
+
+import Test.Framework
+  ( Test
+  , testGroup
+  )
+import Test.Framework.Providers.HUnit
+  ( testCase
+  )
+import Test.HUnit
+  ( assertEqual
+  )
+import Data.Text
+  ( Text
+  )
+import qualified Data.Text as T
+  ( pack
+  )
+import Zenacy.HTML
+
+testIssues :: Test
+testIssues = testGroup "Issues"
+  [ testIssue01
+  ]
+
+testIssue01 :: Test
+testIssue01 = testCase "issue 01" $ do
+  flip (assertEqual "Issue 1 case 1")
+    (htmlRender $ htmlParseEasy
+    "<html><body> <p><i><i>a<i>b<i></i></i></i></i></p> </body></html>")
+    "<html><head></head><body> <p><i><i>a<i>b<i></i></i></i></i></p> </body></html>"
+  flip (assertEqual "Issue 1 case 2")
+    (htmlRender $ htmlParseEasy
+    "<html><body>x<p><i><i>a<i>b<i></i></i></i></i></p>y</body></html>")
+    "<html><head></head><body>x<p><i><i>a<i>b<i></i></i></i></i></p>y</body></html>"
diff --git a/test/TestSuite.hs b/test/TestSuite.hs
--- a/test/TestSuite.hs
+++ b/test/TestSuite.hs
@@ -1,5 +1,7 @@
 module Main where
 
+import Examples
+import Issues
 import Samples
 import Zenacy.HTML.Internal.Buffer.Tests
 import Zenacy.HTML.Internal.Entity.Tests
@@ -29,5 +31,7 @@
   , testTrie
   , testZip
   , testQuery
+  , testExamples
   , testSamples
+  , testIssues
   ]
diff --git a/zenacy-html.cabal b/zenacy-html.cabal
--- a/zenacy-html.cabal
+++ b/zenacy-html.cabal
@@ -1,5 +1,5 @@
 cabal-version: >= 1.10
-version: 2.0.7
+version: 2.1.0
 name:
   zenacy-html
 synopsis:
@@ -149,7 +149,10 @@
   default-language:
     Haskell2010
   other-modules:
-    Zenacy.HTML.Internal.Buffer.Tests
+    Examples
+    , Issues
+    , Samples
+    , Zenacy.HTML.Internal.Buffer.Tests
     , Zenacy.HTML.Internal.Entity.Tests
     , Zenacy.HTML.Internal.HTML.Tests
     , Zenacy.HTML.Internal.Image.Tests
@@ -160,7 +163,6 @@
     , Zenacy.HTML.Internal.Token.Tests
     , Zenacy.HTML.Internal.Trie.Tests
     , Zenacy.HTML.Internal.Zip.Tests
-    , Samples
 
 benchmark zenacy-html-bench
   type: