diff --git a/12/style.css b/12/style.css
index 463a79f..e614995 100644
--- a/12/style.css
+++ b/12/style.css
@@ -216,6 +216,10 @@ a:hover{
   	margin-bottom: 20px;
 }
 
+#shell_03.hidden {
+display:none;
+}
+
 #shell_03 iframe {
   width: 100%;
   height: 100%;