function changeBanner()
{
var img_rnd = new Array ("images/img1.jpg", "images/img2.jpg", "images/img3.jpg",  "images/img4.jpg", "images/img5.jpg", "images/img6.jpg", "images/img7.jpg");
var i = Math.round(6*Math.random());
  //document.banner.src = img_rnd[i];
  document.getElementById('banner').style.background = "url("+img_rnd[i]+")";
  }