diff --git a/content/html/style/src/nsCSSDeclaration.cpp b/content/html/style/src/nsCSSDeclaration.cpp
index 8fe5137809b8..1d4cfc12261f 100644
--- a/content/html/style/src/nsCSSDeclaration.cpp
+++ b/content/html/style/src/nsCSSDeclaration.cpp
@@ -389,6 +389,7 @@ void nsCSSColor::List(FILE* out, PRInt32 aIndent) const
   mBackFilter.AppendToString(buffer, PROP_BACKGROUND_FILTER);
   mCursor.AppendToString(buffer, PROP_CURSOR);
   mCursorImage.AppendToString(buffer, PROP_CURSOR_IMAGE);
+  mOpacity.AppendToString(buffer, PROP_OPACITY);
   fputs(buffer, out);
 }
 
@@ -781,6 +782,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull == mColor) {
         mColor = new nsCSSColor();
       }
@@ -796,6 +798,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
           case PROP_BACKGROUND_FILTER:      mColor->mBackFilter = aValue;      break;
           case PROP_CURSOR:                 mColor->mCursor = aValue;          break;
           case PROP_CURSOR_IMAGE:           mColor->mCursorImage = aValue;     break;
+          case PROP_OPACITY:                mColor->mOpacity = aValue;         break;
         }
       }
       else {
@@ -1138,6 +1141,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull != mColor) {
         switch (aProperty) {
           case PROP_COLOR:                  aValue = mColor->mColor;           break;
@@ -1150,6 +1154,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
           case PROP_BACKGROUND_FILTER:      aValue = mColor->mBackFilter;      break;
           case PROP_CURSOR:                 aValue = mColor->mCursor;          break;
           case PROP_CURSOR_IMAGE:           aValue = mColor->mCursorImage;     break;
+          case PROP_OPACITY:                aValue = mColor->mOpacity;         break;
         }
       }
       else {
diff --git a/content/html/style/src/nsCSSParser.cpp b/content/html/style/src/nsCSSParser.cpp
index 2c23dbcfdac4..d3fa2b38c097 100644
--- a/content/html/style/src/nsCSSParser.cpp
+++ b/content/html/style/src/nsCSSParser.cpp
@@ -1099,6 +1099,7 @@ CSSParserImpl::ParseDeclaration(PRInt32* aErrorCode,
 #define VARIANT_CK   (VARIANT_COLOR | VARIANT_KEYWORD)
 #define VARIANT_C    VARIANT_COLOR
 #define VARIANT_UK   (VARIANT_URL | VARIANT_KEYWORD)
+#define VARIANT_HPN  (VARIANT_INHERIT | VARIANT_PERCENT | VARIANT_NUMBER)
 
 // Keyword id tables for variant/enum parsing
 static PRInt32 kBackgroundAttachmentKTable[] = {
@@ -1685,6 +1686,8 @@ PRBool CSSParserImpl::ParseProperty(PRInt32* aErrorCode,
   case PROP_PADDING_RIGHT:
   case PROP_PADDING_TOP:
     return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_LP, nsnull);
+  case PROP_OPACITY:
+    return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_HPN, nsnull);
   case PROP_OVERFLOW:
     return ParseEnum(aErrorCode, aDeclaration, aName, kOverflowKTable);
   case PROP_POSITION:
diff --git a/content/html/style/src/nsCSSStruct.cpp b/content/html/style/src/nsCSSStruct.cpp
index 8fe5137809b8..1d4cfc12261f 100644
--- a/content/html/style/src/nsCSSStruct.cpp
+++ b/content/html/style/src/nsCSSStruct.cpp
@@ -389,6 +389,7 @@ void nsCSSColor::List(FILE* out, PRInt32 aIndent) const
   mBackFilter.AppendToString(buffer, PROP_BACKGROUND_FILTER);
   mCursor.AppendToString(buffer, PROP_CURSOR);
   mCursorImage.AppendToString(buffer, PROP_CURSOR_IMAGE);
+  mOpacity.AppendToString(buffer, PROP_OPACITY);
   fputs(buffer, out);
 }
 
@@ -781,6 +782,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull == mColor) {
         mColor = new nsCSSColor();
       }
@@ -796,6 +798,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
           case PROP_BACKGROUND_FILTER:      mColor->mBackFilter = aValue;      break;
           case PROP_CURSOR:                 mColor->mCursor = aValue;          break;
           case PROP_CURSOR_IMAGE:           mColor->mCursorImage = aValue;     break;
+          case PROP_OPACITY:                mColor->mOpacity = aValue;         break;
         }
       }
       else {
@@ -1138,6 +1141,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull != mColor) {
         switch (aProperty) {
           case PROP_COLOR:                  aValue = mColor->mColor;           break;
@@ -1150,6 +1154,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
           case PROP_BACKGROUND_FILTER:      aValue = mColor->mBackFilter;      break;
           case PROP_CURSOR:                 aValue = mColor->mCursor;          break;
           case PROP_CURSOR_IMAGE:           aValue = mColor->mCursorImage;     break;
+          case PROP_OPACITY:                aValue = mColor->mOpacity;         break;
         }
       }
       else {
diff --git a/content/html/style/src/nsCSSStyleRule.cpp b/content/html/style/src/nsCSSStyleRule.cpp
index 584cc8c30a8c..e4c66be6dd82 100644
--- a/content/html/style/src/nsCSSStyleRule.cpp
+++ b/content/html/style/src/nsCSSStyleRule.cpp
@@ -843,6 +843,25 @@ void CSSStyleRuleImpl::MapStyleInto(nsIStyleContext* aContext, nsIPresContext* a
           color->mBackgroundFlags &= ~NS_STYLE_BG_Y_POSITION_PERCENT;
         }
 
+        // opacity: factor, percent, enum
+        if (ourColor->mOpacity.GetUnit() == eCSSUnit_Percent) {
+          color->mOpacity.SetPercentValue(ourColor->mOpacity.GetPercentValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Number) {
+          color->mOpacity.SetFactorValue(ourColor->mOpacity.GetFloatValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Enumerated) {
+          // Only enum value is inherit
+          nsStyleColor* parentColor = color;
+          nsIStyleContext* parentContext = aContext->GetParent();
+          if (nsnull != parentContext) {
+            parentColor = (nsStyleColor*)parentContext->GetData(eStyleStruct_Color);
+            color->mOpacity = parentColor->mOpacity;
+            NS_RELEASE(parentContext);
+          }
+          
+        }
+
   // XXX: NYI        nsCSSValue mBackFilter;
       }
     }
diff --git a/content/html/style/src/nsICSSDeclaration.h b/content/html/style/src/nsICSSDeclaration.h
index 827fe2aa9f84..b662854f001d 100644
--- a/content/html/style/src/nsICSSDeclaration.h
+++ b/content/html/style/src/nsICSSDeclaration.h
@@ -230,6 +230,7 @@ struct nsCSSColor : public nsCSSStruct  {
   nsCSSValue mBackFilter;
   nsCSSValue mCursor;
   nsCSSValue mCursorImage;
+  nsCSSValue mOpacity;
 };
 
 struct nsCSSText : public nsCSSStruct  {
diff --git a/layout/html/style/src/nsCSSDeclaration.cpp b/layout/html/style/src/nsCSSDeclaration.cpp
index 8fe5137809b8..1d4cfc12261f 100644
--- a/layout/html/style/src/nsCSSDeclaration.cpp
+++ b/layout/html/style/src/nsCSSDeclaration.cpp
@@ -389,6 +389,7 @@ void nsCSSColor::List(FILE* out, PRInt32 aIndent) const
   mBackFilter.AppendToString(buffer, PROP_BACKGROUND_FILTER);
   mCursor.AppendToString(buffer, PROP_CURSOR);
   mCursorImage.AppendToString(buffer, PROP_CURSOR_IMAGE);
+  mOpacity.AppendToString(buffer, PROP_OPACITY);
   fputs(buffer, out);
 }
 
@@ -781,6 +782,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull == mColor) {
         mColor = new nsCSSColor();
       }
@@ -796,6 +798,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
           case PROP_BACKGROUND_FILTER:      mColor->mBackFilter = aValue;      break;
           case PROP_CURSOR:                 mColor->mCursor = aValue;          break;
           case PROP_CURSOR_IMAGE:           mColor->mCursorImage = aValue;     break;
+          case PROP_OPACITY:                mColor->mOpacity = aValue;         break;
         }
       }
       else {
@@ -1138,6 +1141,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull != mColor) {
         switch (aProperty) {
           case PROP_COLOR:                  aValue = mColor->mColor;           break;
@@ -1150,6 +1154,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
           case PROP_BACKGROUND_FILTER:      aValue = mColor->mBackFilter;      break;
           case PROP_CURSOR:                 aValue = mColor->mCursor;          break;
           case PROP_CURSOR_IMAGE:           aValue = mColor->mCursorImage;     break;
+          case PROP_OPACITY:                aValue = mColor->mOpacity;         break;
         }
       }
       else {
diff --git a/layout/html/style/src/nsCSSParser.cpp b/layout/html/style/src/nsCSSParser.cpp
index 2c23dbcfdac4..d3fa2b38c097 100644
--- a/layout/html/style/src/nsCSSParser.cpp
+++ b/layout/html/style/src/nsCSSParser.cpp
@@ -1099,6 +1099,7 @@ CSSParserImpl::ParseDeclaration(PRInt32* aErrorCode,
 #define VARIANT_CK   (VARIANT_COLOR | VARIANT_KEYWORD)
 #define VARIANT_C    VARIANT_COLOR
 #define VARIANT_UK   (VARIANT_URL | VARIANT_KEYWORD)
+#define VARIANT_HPN  (VARIANT_INHERIT | VARIANT_PERCENT | VARIANT_NUMBER)
 
 // Keyword id tables for variant/enum parsing
 static PRInt32 kBackgroundAttachmentKTable[] = {
@@ -1685,6 +1686,8 @@ PRBool CSSParserImpl::ParseProperty(PRInt32* aErrorCode,
   case PROP_PADDING_RIGHT:
   case PROP_PADDING_TOP:
     return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_LP, nsnull);
+  case PROP_OPACITY:
+    return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_HPN, nsnull);
   case PROP_OVERFLOW:
     return ParseEnum(aErrorCode, aDeclaration, aName, kOverflowKTable);
   case PROP_POSITION:
diff --git a/layout/html/style/src/nsCSSStyleRule.cpp b/layout/html/style/src/nsCSSStyleRule.cpp
index 584cc8c30a8c..e4c66be6dd82 100644
--- a/layout/html/style/src/nsCSSStyleRule.cpp
+++ b/layout/html/style/src/nsCSSStyleRule.cpp
@@ -843,6 +843,25 @@ void CSSStyleRuleImpl::MapStyleInto(nsIStyleContext* aContext, nsIPresContext* a
           color->mBackgroundFlags &= ~NS_STYLE_BG_Y_POSITION_PERCENT;
         }
 
+        // opacity: factor, percent, enum
+        if (ourColor->mOpacity.GetUnit() == eCSSUnit_Percent) {
+          color->mOpacity.SetPercentValue(ourColor->mOpacity.GetPercentValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Number) {
+          color->mOpacity.SetFactorValue(ourColor->mOpacity.GetFloatValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Enumerated) {
+          // Only enum value is inherit
+          nsStyleColor* parentColor = color;
+          nsIStyleContext* parentContext = aContext->GetParent();
+          if (nsnull != parentContext) {
+            parentColor = (nsStyleColor*)parentContext->GetData(eStyleStruct_Color);
+            color->mOpacity = parentColor->mOpacity;
+            NS_RELEASE(parentContext);
+          }
+          
+        }
+
   // XXX: NYI        nsCSSValue mBackFilter;
       }
     }
diff --git a/layout/html/style/src/nsICSSDeclaration.h b/layout/html/style/src/nsICSSDeclaration.h
index 827fe2aa9f84..b662854f001d 100644
--- a/layout/html/style/src/nsICSSDeclaration.h
+++ b/layout/html/style/src/nsICSSDeclaration.h
@@ -230,6 +230,7 @@ struct nsCSSColor : public nsCSSStruct  {
   nsCSSValue mBackFilter;
   nsCSSValue mCursor;
   nsCSSValue mCursorImage;
+  nsCSSValue mOpacity;
 };
 
 struct nsCSSText : public nsCSSStruct  {
diff --git a/layout/style/nsCSSDeclaration.cpp b/layout/style/nsCSSDeclaration.cpp
index 8fe5137809b8..1d4cfc12261f 100644
--- a/layout/style/nsCSSDeclaration.cpp
+++ b/layout/style/nsCSSDeclaration.cpp
@@ -389,6 +389,7 @@ void nsCSSColor::List(FILE* out, PRInt32 aIndent) const
   mBackFilter.AppendToString(buffer, PROP_BACKGROUND_FILTER);
   mCursor.AppendToString(buffer, PROP_CURSOR);
   mCursorImage.AppendToString(buffer, PROP_CURSOR_IMAGE);
+  mOpacity.AppendToString(buffer, PROP_OPACITY);
   fputs(buffer, out);
 }
 
@@ -781,6 +782,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull == mColor) {
         mColor = new nsCSSColor();
       }
@@ -796,6 +798,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
           case PROP_BACKGROUND_FILTER:      mColor->mBackFilter = aValue;      break;
           case PROP_CURSOR:                 mColor->mCursor = aValue;          break;
           case PROP_CURSOR_IMAGE:           mColor->mCursorImage = aValue;     break;
+          case PROP_OPACITY:                mColor->mOpacity = aValue;         break;
         }
       }
       else {
@@ -1138,6 +1141,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull != mColor) {
         switch (aProperty) {
           case PROP_COLOR:                  aValue = mColor->mColor;           break;
@@ -1150,6 +1154,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
           case PROP_BACKGROUND_FILTER:      aValue = mColor->mBackFilter;      break;
           case PROP_CURSOR:                 aValue = mColor->mCursor;          break;
           case PROP_CURSOR_IMAGE:           aValue = mColor->mCursorImage;     break;
+          case PROP_OPACITY:                aValue = mColor->mOpacity;         break;
         }
       }
       else {
diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 2c23dbcfdac4..d3fa2b38c097 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -1099,6 +1099,7 @@ CSSParserImpl::ParseDeclaration(PRInt32* aErrorCode,
 #define VARIANT_CK   (VARIANT_COLOR | VARIANT_KEYWORD)
 #define VARIANT_C    VARIANT_COLOR
 #define VARIANT_UK   (VARIANT_URL | VARIANT_KEYWORD)
+#define VARIANT_HPN  (VARIANT_INHERIT | VARIANT_PERCENT | VARIANT_NUMBER)
 
 // Keyword id tables for variant/enum parsing
 static PRInt32 kBackgroundAttachmentKTable[] = {
@@ -1685,6 +1686,8 @@ PRBool CSSParserImpl::ParseProperty(PRInt32* aErrorCode,
   case PROP_PADDING_RIGHT:
   case PROP_PADDING_TOP:
     return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_LP, nsnull);
+  case PROP_OPACITY:
+    return ParseVariant(aErrorCode, aDeclaration, aName, VARIANT_HPN, nsnull);
   case PROP_OVERFLOW:
     return ParseEnum(aErrorCode, aDeclaration, aName, kOverflowKTable);
   case PROP_POSITION:
diff --git a/layout/style/nsCSSStruct.cpp b/layout/style/nsCSSStruct.cpp
index 8fe5137809b8..1d4cfc12261f 100644
--- a/layout/style/nsCSSStruct.cpp
+++ b/layout/style/nsCSSStruct.cpp
@@ -389,6 +389,7 @@ void nsCSSColor::List(FILE* out, PRInt32 aIndent) const
   mBackFilter.AppendToString(buffer, PROP_BACKGROUND_FILTER);
   mCursor.AppendToString(buffer, PROP_CURSOR);
   mCursorImage.AppendToString(buffer, PROP_CURSOR_IMAGE);
+  mOpacity.AppendToString(buffer, PROP_OPACITY);
   fputs(buffer, out);
 }
 
@@ -781,6 +782,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull == mColor) {
         mColor = new nsCSSColor();
       }
@@ -796,6 +798,7 @@ nsresult CSSDeclarationImpl::AddValue(PRInt32 aProperty, const nsCSSValue& aValu
           case PROP_BACKGROUND_FILTER:      mColor->mBackFilter = aValue;      break;
           case PROP_CURSOR:                 mColor->mCursor = aValue;          break;
           case PROP_CURSOR_IMAGE:           mColor->mCursorImage = aValue;     break;
+          case PROP_OPACITY:                mColor->mOpacity = aValue;         break;
         }
       }
       else {
@@ -1138,6 +1141,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
     case PROP_BACKGROUND_FILTER:
     case PROP_CURSOR:
     case PROP_CURSOR_IMAGE:
+    case PROP_OPACITY:
       if (nsnull != mColor) {
         switch (aProperty) {
           case PROP_COLOR:                  aValue = mColor->mColor;           break;
@@ -1150,6 +1154,7 @@ nsresult CSSDeclarationImpl::GetValue(PRInt32 aProperty, nsCSSValue& aValue)
           case PROP_BACKGROUND_FILTER:      aValue = mColor->mBackFilter;      break;
           case PROP_CURSOR:                 aValue = mColor->mCursor;          break;
           case PROP_CURSOR_IMAGE:           aValue = mColor->mCursorImage;     break;
+          case PROP_OPACITY:                aValue = mColor->mOpacity;         break;
         }
       }
       else {
diff --git a/layout/style/nsCSSStyleRule.cpp b/layout/style/nsCSSStyleRule.cpp
index 584cc8c30a8c..e4c66be6dd82 100644
--- a/layout/style/nsCSSStyleRule.cpp
+++ b/layout/style/nsCSSStyleRule.cpp
@@ -843,6 +843,25 @@ void CSSStyleRuleImpl::MapStyleInto(nsIStyleContext* aContext, nsIPresContext* a
           color->mBackgroundFlags &= ~NS_STYLE_BG_Y_POSITION_PERCENT;
         }
 
+        // opacity: factor, percent, enum
+        if (ourColor->mOpacity.GetUnit() == eCSSUnit_Percent) {
+          color->mOpacity.SetPercentValue(ourColor->mOpacity.GetPercentValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Number) {
+          color->mOpacity.SetFactorValue(ourColor->mOpacity.GetFloatValue());
+        }
+        else if (ourColor->mOpacity.GetUnit() == eCSSUnit_Enumerated) {
+          // Only enum value is inherit
+          nsStyleColor* parentColor = color;
+          nsIStyleContext* parentContext = aContext->GetParent();
+          if (nsnull != parentContext) {
+            parentColor = (nsStyleColor*)parentContext->GetData(eStyleStruct_Color);
+            color->mOpacity = parentColor->mOpacity;
+            NS_RELEASE(parentContext);
+          }
+          
+        }
+
   // XXX: NYI        nsCSSValue mBackFilter;
       }
     }