적용화면

Source

HTML

<img id="banner" src="" alt="" width="100%" />

JavaScript

var banner = new Array();
banner[banner.length] = 'https://goo.gl/1p6EFv';
banner[banner.length] = 'https://goo.gl/BoFkox';
banner[banner.length] = 'https://goo.gl/Cdu4cD';

var elem = document.getElementById('banner');
var size = Math.floor(Math.random()*(banner.length));
size = (isNaN(size)) ? 0 : size;
elem.setAttribute('src', banner[size]);