The new schema.org by Google, Yahoo and MS recommends usage of the attribute to display the status of products in an online shop:
&
As noted by the others <link>
can be used in the body, but only sometimes. In those cases it's referred to as "body-ok". Here's a list of which link types are body-ok: https://html.spec.whatwg.org/multipage/links.html#body-ok
As of 20 June 2018 the following can be used in the body:
<body>
<link rel="dns-prefetch">
<link rel="modulepreload">
<link rel="pingback">
<link rel="preconnect">
<link rel="prefetch">
<link rel="preload">
<link rel="prerender">
<link rel="stylesheet">
</body>