Web Design in a Nutshell, 3rd Edition

insertBefore( )

Well, in that case, we can use the insertBefore( ) method.

var body = document.getElementsByTagName( 'body' )[0];
body.insertBefore( new_div, body.firstChild );

insertBefore( ) takes two arguments: the first is the node you want to insert, and the second is the node you want to insert it in front of. In our example, we are inserting the new div in front of the firstChild of the body element.