diff --git a/user_guide/libraries/output.html b/user_guide/libraries/output.html
index 827cc8b..1905f32 100644
--- a/user_guide/libraries/output.html
+++ b/user_guide/libraries/output.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-<html>
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
 <head>
 
 <title>CodeIgniter User Guide : Output Class</title>