diff --git a/_keysnail.js b/_keysnail.js
index 27f820b..dc53375 100644
--- a/_keysnail.js
+++ b/_keysnail.js
@@ -199,17 +199,19 @@ ext.add("strong-fullscreen", function(){
     }
 
     var tabs = document.getElementById("verticaltabs-box");
-    var pref_key = "extensions.verticaltabs.width";
-    var pref_key_bak = pref_key + "_bak"
-    if(isfullscreen){
-        var width_orig = util.getIntPref(pref_key);
-        util.setIntPref(pref_key_bak, width_orig);
-        util.setIntPref(pref_key, 0);
-        tabs.setAttribute("width", "0");
-    }else if(parseInt(tabs.getAttribute("width") || "") === 0){
-        var width_bak = util.getIntPref(pref_key_bak);
-        util.setIntPref(pref_key, width_bak);
-        tabs.setAttribute("width", width_bak.toString());
+    if(tabs){ 
+        var pref_key = "extensions.verticaltabs.width";
+        var pref_key_bak = pref_key + "_bak"
+        if(isfullscreen){
+            var width_orig = util.getIntPref(pref_key);
+            util.setIntPref(pref_key_bak, width_orig);
+            util.setIntPref(pref_key, 0);
+            tabs.setAttribute("width", "0");
+        }else if(parseInt(tabs.getAttribute("width") || "") === 0){
+            var width_bak = util.getIntPref(pref_key_bak);
+            util.setIntPref(pref_key, width_bak);
+            tabs.setAttribute("width", width_bak.toString());
+        }
     }
 
 }, "go fullscreen with hiding toolbar and tabbar");
diff --git a/emacs.el b/emacs.el
index a0b9178..4adb37a 100644
--- a/emacs.el
+++ b/emacs.el
@@ -345,7 +345,13 @@ drill-instructor.el"
             ))
 
 (when (require 'whitespace nil t)
-  (setq whitespace-style '(face newline newline-mark empty lines-trail trailing))
+  (setq whitespace-style '(face
+                           trailing     ; trailing blanks
+                           newline      ; newlines
+                           newline-mark ; use display table for newline
+                           empty        ; empty lines at beg or end of buffer
+                           lines-tail  ; lines over 80
+                           ))
   ;; (setq whitespace-newline 'font-lock-comment-face)
   (add-to-list 'whitespace-display-mappings
                `(newline-mark ?\n ,(vconcat "$\n"))