// JavaScript Document

mypics = Array("images/top-image-01.jpg", "images/top-image-02.jpg", "images/top-image-03.jpg", "images/top-image-04.jpg");
randomnumber = Math.floor( Math.random() * mypics.length );
document.getElementById('headerSub').style.backgroundImage = "url(" + mypics[randomnumber] + ")";