--- a/browser/modules/PanelFrame.jsm
+++ b/browser/modules/PanelFrame.jsm
@@ -45,17 +45,17 @@ let PanelFrameInternal = {
    * @param {String} aSize The initial size of the panel (width and height are the same
    *                       if specified).
    */
   _attachNotificatonPanel: function(aWindow, aParent, aButton, aType, aOrigin, aSrc, aSize) {
     aParent.hidden = false;
     let notificationFrameId = aOrigin ? aType + "-status-" + aOrigin : aType;
     let frame = aWindow.document.getElementById(notificationFrameId);
 
-    // If the button was customized to a new location, we we'll destroy the
+    // If the button was customized to a new location, destroy the
     // iframe and start fresh.
     if (frame && frame.parentNode != aParent) {
       SharedFrame.forgetGroup(frame.id);
       frame.parentNode.removeChild(frame);
       frame = null;
     }
 
     if (!frame) {
@@ -152,28 +152,28 @@ let PanelFrame = {
         dynamicResizer.stop();
       notificationFrame.docShell.isActive = false;
       dispatchPanelEvent(aType + "FrameHide");
     });
 
     panel.addEventListener("popupshown", function onpopupshown() {
       panel.removeEventListener("popupshown", onpopupshown);
       SharedFrame.setOwner(notificationFrameId, notificationFrame);
-      // This attribute is needed on both the button and the
-      // containing toolbaritem since the buttons on OS X have
-      // moz-appearance:none, while their container gets
-      // moz-appearance:toolbarbutton due to the way that toolbar buttons
-      // get combined on OS X.
       let initFrameShow = () => {
         notificationFrame.docShell.isActive = true;
         notificationFrame.docShell.isAppTab = true;
         if (dynamicResizer)
           dynamicResizer.start(panel, notificationFrame);
         dispatchPanelEvent(aType + "FrameShow");
       };
+      // This attribute is needed on both the button and the
+      // containing toolbaritem since the buttons on OS X have
+      // moz-appearance:none, while their container gets
+      // moz-appearance:toolbarbutton due to the way that toolbar buttons
+      // get combined on OS X.
       anchorBtn.setAttribute("open", "true");
       if (notificationFrame.contentDocument &&
           notificationFrame.contentDocument.readyState == "complete") {
         initFrameShow();
       } else {
         // first time load, wait for load and dispatch after load
         notificationFrame.addEventListener("load", function panelBrowserOnload(e) {
           notificationFrame.removeEventListener("load", panelBrowserOnload, true);

--- a/browser/modules/Social.jsm
+++ b/browser/modules/Social.jsm
@@ -416,23 +416,27 @@ function sizeSocialPanelToContent(panel,
   // if the panel is preloaded prior to being shown, cs will be null.  in that
   // case use the minimum size for the panel until it is shown.
   if (cs) {
     let computedHeight = parseInt(cs.marginTop) + body.offsetHeight + parseInt(cs.marginBottom);
     height = Math.max(computedHeight, height);
     let computedWidth = parseInt(cs.marginLeft) + body.offsetWidth + parseInt(cs.marginRight);
     width = Math.max(computedWidth, width);
   }
-  // add extra space the panel needs if any
-  width += panel.boxObject.width - iframe.boxObject.width;
-  height += panel.boxObject.height - iframe.boxObject.height;
+
+  // only add the extra space if the iframe has been loaded
+  if (iframe.boxObject.width && iframe.boxObject.height) {
+    // add extra space the panel needs if any
+    width += panel.boxObject.width - iframe.boxObject.width;
+    height += panel.boxObject.height - iframe.boxObject.height;
+  }
 
   // when size is computed, we want to be sure changes are "significant" since
   // some sites will resize when the iframe is resized by a small amount, making
-  // the panel slowely shrink to some minimum.
+  // the panel slowly shrink to some minimum.
   if (Math.abs(panel.boxObject.width - width) > 2 || Math.abs(panel.boxObject.height - height) > 2) {
     panel.sizeTo(width, height);
   }
 }
 
 function DynamicResizeWatcher() {
   this._mutationObserver = null;
 }