diff --git a/doc/docs.html b/doc/docs.html
index 998b6f4..67ce9d8 100644
--- a/doc/docs.html
+++ b/doc/docs.html
@@ -1,4 +1,4 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
 <html>
 <head>
 <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">