The default (fallback) embedded content is all in English; make the root html element reflect that. It may make more hacks with lang attributes simpler to be able to always assume it is meaningful.
@@ -1,5 +1,5 @@
<!DOCTYPE html>
-<html>
+<html lang="en">
<head>
<link rel="stylesheet" href="max80.css" />
<title class="config">MAX80: Configuration</title>
<title class="status">MAX80</title>
<title class="update">MAX80: Update</title>