diff --git a/index.html b/index.html
index 42969156..e5e2faa3 100644
--- a/index.html
+++ b/index.html
@@ -32,7 +32,7 @@
 
         .framebox, iframe {
             width: 100%;
-            height: 100vh;
+            height: calc(100% - 40px);
             margin: 0;
             padding: 0;
             border: none;