diff --git a/index.html b/index.html
index db8f814..11e77f0 100644
--- a/index.html
+++ b/index.html
@@ -1,5 +1,5 @@
 <!doctype html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8">
     <title>HTTP Caching Tests</title>
