diff --git a/google-r-style.html b/google-r-style.html
index d5d600c..8bb7ed7 100755
--- a/google-r-style.html
+++ b/google-r-style.html
@@ -1,3 +1,5 @@
+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/REC-html4/strict.dtd">
 <html>
   <head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">