diff --git a/content/base/src/nsContentUtils.cpp b/content/base/src/nsContentUtils.cpp
index 3584d5f94ec5..ac8a43331349 100644
--- a/content/base/src/nsContentUtils.cpp
+++ b/content/base/src/nsContentUtils.cpp
@@ -5136,7 +5136,7 @@ nsContentUtils::GetViewportInfo(nsIDocument *aDocument)
   nsresult errorCode;
   float scaleMinFloat = minScaleStr.ToFloat(&errorCode);
 
-  if (errorCode) {
+  if (NS_FAILED(errorCode)) {
     scaleMinFloat = kViewportMinScale;
   }
 
@@ -5151,7 +5151,7 @@ nsContentUtils::GetViewportInfo(nsIDocument *aDocument)
   nsresult scaleMaxErrorCode;
   float scaleMaxFloat = maxScaleStr.ToFloat(&scaleMaxErrorCode);
 
-  if (scaleMaxErrorCode) {
+  if (NS_FAILED(scaleMaxErrorCode)) {
     scaleMaxFloat = kViewportMaxScale;
   }
 
@@ -5210,7 +5210,7 @@ nsContentUtils::GetViewportInfo(nsIDocument *aDocument)
   screen->GetRect(&screenLeft, &screenTop, &screenWidth, &screenHeight);
 
   uint32_t width = widthStr.ToInteger(&errorCode);
-  if (errorCode) {
+  if (NS_FAILED(errorCode)) {
     if (autoSize) {
       width = screenWidth;
     } else {
@@ -5229,7 +5229,7 @@ nsContentUtils::GetViewportInfo(nsIDocument *aDocument)
 
   uint32_t height = heightStr.ToInteger(&errorCode);
 
-  if (errorCode) {
+  if (NS_FAILED(errorCode)) {
     height = width * ((float)screenHeight / screenWidth);
   }
 
@@ -5244,10 +5244,10 @@ nsContentUtils::GetViewportInfo(nsIDocument *aDocument)
 
   // We need to perform a conversion, but only if the initial or maximum
   // scale were set explicitly by the user.
-  if (!scaleStr.IsEmpty() && !scaleErrorCode) {
+  if (!scaleStr.IsEmpty() && NS_SUCCEEDED(scaleErrorCode)) {
     width = NS_MAX(width, (uint32_t)(screenWidth / scaleFloat));
     height = NS_MAX(height, (uint32_t)(screenHeight / scaleFloat));
-  } else if (!maxScaleStr.IsEmpty() && !scaleMaxErrorCode) {
+  } else if (!maxScaleStr.IsEmpty() && NS_SUCCEEDED(scaleMaxErrorCode)) {
     width = NS_MAX(width, (uint32_t)(screenWidth / scaleMaxFloat));
     height = NS_MAX(height, (uint32_t)(screenHeight / scaleMaxFloat));
   }
diff --git a/content/html/content/src/nsHTMLFrameSetElement.cpp b/content/html/content/src/nsHTMLFrameSetElement.cpp
index 12a04ee8bd35..8435502e6730 100644
--- a/content/html/content/src/nsHTMLFrameSetElement.cpp
+++ b/content/html/content/src/nsHTMLFrameSetElement.cpp
@@ -277,7 +277,7 @@ nsHTMLFrameSetElement::ParseRowCol(const nsAString & aValue,
         // Otherwise just convert to integer.
         nsresult err;
         specs[i].mValue = token.ToInteger(&err);
-        if (err) {
+        if (NS_FAILED(err)) {
           specs[i].mValue = 0;
         }
       }
diff --git a/content/xul/templates/src/nsXULContentBuilder.cpp b/content/xul/templates/src/nsXULContentBuilder.cpp
index 3597d8ccb0de..59154ecf8fe6 100644
--- a/content/xul/templates/src/nsXULContentBuilder.cpp
+++ b/content/xul/templates/src/nsXULContentBuilder.cpp
@@ -1891,7 +1891,7 @@ nsXULContentBuilder::InsertSortedNode(nsIContent* aContainer,
             // found "static" XUL element count hint
             nsresult strErr = NS_OK;
             staticCount = staticValue.ToInteger(&strErr);
-            if (strErr)
+            if (NS_FAILED(strErr))
                 staticCount = 0;
         } else {
             // compute the "static" XUL element count
diff --git a/js/xpconnect/src/XPCWrappedNative.cpp b/js/xpconnect/src/XPCWrappedNative.cpp
index 27ef5d96c7f7..7d226726ede5 100644
--- a/js/xpconnect/src/XPCWrappedNative.cpp
+++ b/js/xpconnect/src/XPCWrappedNative.cpp
@@ -551,8 +551,8 @@ XPCWrappedNative::GetNewOrUsed(XPCCallContext& ccx,
             JSObject *cached = cache->GetWrapper();
             if (cached) {
                 if (IS_SLIM_WRAPPER_OBJECT(cached)) {
-                    if (!XPCWrappedNative::Morph(ccx, cached, Interface, cache,
-                                                 getter_AddRefs(wrapper)))
+                    if (NS_FAILED(XPCWrappedNative::Morph(ccx, cached,
+                          Interface, cache, getter_AddRefs(wrapper))))
                         return NS_ERROR_FAILURE;
                 } else {
                     wrapper = static_cast<XPCWrappedNative*>(xpc_GetJSPrivate(cached));
diff --git a/layout/forms/nsListControlFrame.cpp b/layout/forms/nsListControlFrame.cpp
index 197a9bfc36c7..2749435206fc 100644
--- a/layout/forms/nsListControlFrame.cpp
+++ b/layout/forms/nsListControlFrame.cpp
@@ -1575,7 +1575,7 @@ nsListControlFrame::GetFormProperty(nsIAtom* aName, nsAString& aValue) const
     nsresult error = NS_OK;
     bool selected = false;
     int32_t indx = val.ToInteger(&error, 10); // Get index from aValue
-    if (error == 0)
+    if (NS_SUCCEEDED(error))
        selected = IsContentSelectedByIndex(indx); 
   
     aValue.Assign(selected ? NS_LITERAL_STRING("1") : NS_LITERAL_STRING("0"));
diff --git a/layout/generic/nsSelection.cpp b/layout/generic/nsSelection.cpp
index b92350931e44..3e3c2c7cfc24 100644
--- a/layout/generic/nsSelection.cpp
+++ b/layout/generic/nsSelection.cpp
@@ -935,7 +935,7 @@ nsFrameSelection::MoveCaret(uint32_t          aKeycode,
                                             aVisualMovement);
 
   if (NS_FAILED(result) || !frame)
-    return result?result:NS_ERROR_FAILURE;
+    return NS_FAILED(result) ? result : NS_ERROR_FAILURE;
 
   //set data using mLimiter to stop on scroll views.  If we have a limiter then we stop peeking
   //when we hit scrollable views.  If no limiter then just let it go ahead
@@ -5567,7 +5567,7 @@ Selection::SelectionLanguageChange(bool aLangRTL)
   uint8_t levelBefore, levelAfter;
   result = GetPresContext(getter_AddRefs(context));
   if (NS_FAILED(result) || !context)
-    return result?result:NS_ERROR_FAILURE;
+    return NS_FAILED(result) ? result : NS_ERROR_FAILURE;
 
   uint8_t level = NS_GET_EMBEDDING_LEVEL(focusFrame);
   int32_t focusOffset = GetFocusOffset();
diff --git a/layout/style/nsFontFaceLoader.cpp b/layout/style/nsFontFaceLoader.cpp
index 2c399b432e56..beddffbd8fd4 100644
--- a/layout/style/nsFontFaceLoader.cpp
+++ b/layout/style/nsFontFaceLoader.cpp
@@ -734,7 +734,7 @@ nsUserFontSet::LogMessage(gfxProxyFontEntry *aProxy,
                                    nsCSSProps::kFontStretchKTable).get(),
         aProxy->mSrcIndex);
 
-  if (aStatus != 0) {
+  if (NS_FAILED(aStatus)) {
     msg.Append(": ");
     switch (aStatus) {
     case NS_ERROR_DOM_BAD_URI: