function advertisement() {
    // Array de imagenes
    var images = new Array
    images[1] = "marketing/imgs/base/litigacion1.gif";
    images[2] = "marketing/imgs/base/litigacion2.gif";
    images[3] = "marketing/imgs/base/litigacion3.gif";
    
    // Array de enlaces
    var links = new Array
    links[1] = "http://www.aranzadi.es/formlitigator";
    links[2] = "http://www.aranzadi.es/formlitigator";
    links[3] = "http://www.aranzadi.es/formlitigator";
	
	 // Array de enlaces
    var targets = new Array;
    targets[1] = "_blank";
    targets[2] = "_blank";
    targets[3] = "_blank";
    
    var randomnumber = Math.floor(Math.random()*(images.length-1)) + 1;
    document.getElementById('advertisement').innerHTML = '<a href="' + links[randomnumber] + '" target="' + targets[randomnumber] + '" title=""><img src="' + images[randomnumber] + '" alt=""></a>';
}