diff --git a/IPython/frontend/html/notebook/static/css/notebook.css b/IPython/frontend/html/notebook/static/css/notebook.css
index 6e8cde6..e014f77 100644
--- a/IPython/frontend/html/notebook/static/css/notebook.css
+++ b/IPython/frontend/html/notebook/static/css/notebook.css
@@ -109,6 +109,7 @@ span#kernel_status {
 }
 
 div#notebook_app {
+    width: 100%;
 }
 
 div#left_panel {
diff --git a/IPython/frontend/html/notebook/static/js/notebook.js b/IPython/frontend/html/notebook/static/js/notebook.js
index 23700bb..afd3527 100644
--- a/IPython/frontend/html/notebook/static/js/notebook.js
+++ b/IPython/frontend/html/notebook/static/js/notebook.js
@@ -25,6 +25,8 @@ var IPython = (function (IPython) {
 
 
     Notebook.prototype.style = function () {
+        // With vbox here Chrome exhibits the CodeMirror scroll bug.
+        // Without the vbox here, Firefox won't scroll the notebook div.
         this.element.addClass('vbox box-flex1 border-box-sizing');
     };