Adding note about vbox related scroll bugs.

IPython/frontend/html/notebook/static/css/notebook.css

@@ -109,6 +109,7 b' span#kernel_status {'
 }
 
 div#notebook_app {
+    width: 100%;
 }
 
 div#left_panel {

IPython/frontend/html/notebook/static/js/notebook.js

@@ -25,6 +25,8 b' 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');
     };