JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mostrarADS"></div>

JavaScript

Imagen = new Array('http://www.rsc.org/images/011107_Leaderboard_728x90px_2_tcm18-201691.gif', 'http://comparegithosting.com/_media/ads728.png','http://playnstuff.com/wp-content/themes/StartWPA/images/728.png');
	
	//Obtenemos un valor al azar
	var X = Math.floor((Math.random() * Imagen.length));

document.getElementById("mostrarADS").innerHTML = '<a href="http://www.google.com.ar" target="_blank"><img src="'+ Imagen[X] +'" border="0"></a>';