There are plenty of examples of how to included content from one html file in another, including this:
Include another HTML file in a HTML file
Is it possible to include content from an other file in the HEAD of the calling html document?
If I try this:
Source
<html>
<head>
<div id="headerInclude"></div>
<script src="/lforms-examples/lib/jquery-1.11.3/jquery.min.js"></script>
<script>$("#headerInclude").load("/lforms-examples/pages/header-footer/ComponentHeader.html");</script>
</head>
<body>
<h1>Basic Questionnaire Example Using Header</h1>
</body>
</html>
Include
<html>
<head>
<link rel="shortcut icon" type="image/x-icon" href="/lforms-examples/img/nachc-favico.png">
</head>
</html>
I get this:
Note the link is in the body and not the head and the favicon.ico is not found.