var currentdate = 0;
var core = 0;

function initArray() {

this.length = initArray.arguments.length;
  for (var i = 0; i < this.length; i++) {
  this[i] = initArray.arguments[i];
  }
}

link = new initArray(
"http://www.ecobus.cl",
"http://www.microventabus.cl",
"http://www.fenabus.cl",
"http://www.ihosting.cl",
"http://www.neutralidadsi.org"
);

image = new initArray(
"http://publicidad.chilebuses.cl/BusesEcobus2007.gif",
"http://publicidad.chilebuses.cl/BannerBusesUsados2.jpg",
"http://publicidad.chilebuses.cl/fenabusbanner.jpg",
"http://publicidad.chilebuses.cl/ihosting.gif",
"http://publicidad.chilebuses.cl/neutralidadsi_animado_468x60.gif"
);

text = new initArray(
"Buses Ecobus",
"Buses Usados",
"Fenabus f.g.",
"iHosting",
"NeutralidadSI!"
);

var currentdate = new Date();
var core = currentdate.getSeconds() % image.length;
var ranlink  = link[core];
var ranimage = image[core];
var rantext  = text[core];

document.write('<div align="center"><target="_blank"><a href=\"' +ranlink+ '\" target="_blank"><img src=\"'+ranimage+'\" border="0" alt=\"'+rantext+'\"></a></div>');