diff --git a/mozilla/content/html/style/src/nsCSSParser.cpp b/mozilla/content/html/style/src/nsCSSParser.cpp
index 0395e2b7e92..60d4a36fb01 100644
--- a/mozilla/content/html/style/src/nsCSSParser.cpp
+++ b/mozilla/content/html/style/src/nsCSSParser.cpp
@@ -1373,6 +1373,7 @@ static PRBool IsPseudoClass(const nsIAtom* aAtom)
                 (nsCSSAtoms::focusPseudo == aAtom) ||
                 (nsCSSAtoms::hoverPseudo == aAtom) ||
                 (nsCSSAtoms::langPseudo == aAtom) ||
+                (nsCSSAtoms::lastChildPseudo == aAtom) ||
                 (nsCSSAtoms::lastNodePseudo == aAtom) ||
                 (nsCSSAtoms::linkPseudo == aAtom) ||
                 (nsCSSAtoms::outOfDatePseudo == aAtom) ||
diff --git a/mozilla/content/html/style/src/nsCSSStyleSheet.cpp b/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
index 79492763fe6..88d1e66d931 100644
--- a/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
+++ b/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
@@ -2980,7 +2980,7 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
           PRInt32 index = -1;
           do {
             parent->ChildAt(++index, firstChild);
-            if (firstChild) { // skip text & comments (and whitespace for firstNode as well)
+            if (firstChild) { // stop at first non-comment and non-whitespace node (and non-text node for firstChild)
               if (IsSignificantChild(firstChild, (nsCSSAtoms::firstNodePseudo == pseudoClass->mAtom))) {
                 break;
               }
@@ -2994,7 +2994,8 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
         result = PRBool(localTrue == (data.mContent == firstChild));
         NS_IF_RELEASE(firstChild);
       }
-      else if (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom) {
+      else if ((nsCSSAtoms::lastChildPseudo == pseudoClass->mAtom) ||
+               (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom)) {
         nsIContent* lastChild = nsnull;
         nsIContent* parent = data.mParentContent;
         if (parent) {
@@ -3002,8 +3003,8 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
           parent->ChildCount(index);
           do {
             parent->ChildAt(--index, lastChild);
-            if (lastChild) { // skip whitespace text & comments
-              if (IsSignificantChild(lastChild, PR_TRUE)) {
+            if (lastChild) { // stop at first non-comment and non-whitespace node (and non-text node for lastChild)
+              if (IsSignificantChild(lastChild, (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom))) {
                 break;
               }
               NS_RELEASE(lastChild);
diff --git a/mozilla/content/shared/public/nsCSSAtomList.h b/mozilla/content/shared/public/nsCSSAtomList.h
index 9aa36e49a9e..c5aa8f806f3 100644
--- a/mozilla/content/shared/public/nsCSSAtomList.h
+++ b/mozilla/content/shared/public/nsCSSAtomList.h
@@ -56,6 +56,7 @@ CSS_ATOM(enabledPseudo, ":enabled")
 
 CSS_ATOM(firstChildPseudo, ":first-child")
 CSS_ATOM(firstNodePseudo, ":first-node")
+CSS_ATOM(lastChildPseudo, ":last-child")
 CSS_ATOM(lastNodePseudo, ":last-node")
 CSS_ATOM(focusPseudo, ":focus")
 
diff --git a/mozilla/layout/style/nsCSSParser.cpp b/mozilla/layout/style/nsCSSParser.cpp
index 0395e2b7e92..60d4a36fb01 100644
--- a/mozilla/layout/style/nsCSSParser.cpp
+++ b/mozilla/layout/style/nsCSSParser.cpp
@@ -1373,6 +1373,7 @@ static PRBool IsPseudoClass(const nsIAtom* aAtom)
                 (nsCSSAtoms::focusPseudo == aAtom) ||
                 (nsCSSAtoms::hoverPseudo == aAtom) ||
                 (nsCSSAtoms::langPseudo == aAtom) ||
+                (nsCSSAtoms::lastChildPseudo == aAtom) ||
                 (nsCSSAtoms::lastNodePseudo == aAtom) ||
                 (nsCSSAtoms::linkPseudo == aAtom) ||
                 (nsCSSAtoms::outOfDatePseudo == aAtom) ||
diff --git a/mozilla/layout/style/nsCSSStyleSheet.cpp b/mozilla/layout/style/nsCSSStyleSheet.cpp
index 79492763fe6..88d1e66d931 100644
--- a/mozilla/layout/style/nsCSSStyleSheet.cpp
+++ b/mozilla/layout/style/nsCSSStyleSheet.cpp
@@ -2980,7 +2980,7 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
           PRInt32 index = -1;
           do {
             parent->ChildAt(++index, firstChild);
-            if (firstChild) { // skip text & comments (and whitespace for firstNode as well)
+            if (firstChild) { // stop at first non-comment and non-whitespace node (and non-text node for firstChild)
               if (IsSignificantChild(firstChild, (nsCSSAtoms::firstNodePseudo == pseudoClass->mAtom))) {
                 break;
               }
@@ -2994,7 +2994,8 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
         result = PRBool(localTrue == (data.mContent == firstChild));
         NS_IF_RELEASE(firstChild);
       }
-      else if (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom) {
+      else if ((nsCSSAtoms::lastChildPseudo == pseudoClass->mAtom) ||
+               (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom)) {
         nsIContent* lastChild = nsnull;
         nsIContent* parent = data.mParentContent;
         if (parent) {
@@ -3002,8 +3003,8 @@ static PRBool SelectorMatches(SelectorMatchesData &data,
           parent->ChildCount(index);
           do {
             parent->ChildAt(--index, lastChild);
-            if (lastChild) { // skip whitespace text & comments
-              if (IsSignificantChild(lastChild, PR_TRUE)) {
+            if (lastChild) { // stop at first non-comment and non-whitespace node (and non-text node for lastChild)
+              if (IsSignificantChild(lastChild, (nsCSSAtoms::lastNodePseudo == pseudoClass->mAtom))) {
                 break;
               }
               NS_RELEASE(lastChild);