:root Selector
Selects the element that is the root of the document.
.root()
In HTML, the root of the document, and thus the element that $(":root") selects, is always the <html> element.
Display the tag name of the root element.
JS
<div id="log">The root of this document is:</div>
CSS
span.fot {
color: red;
font-size: 120%;
font-style: italic;
}
HTML
$("<b></b>").html($(":root")[0].nodeName).appendTo("#log");
DEMO