var Ad = {
 url: '',
 img: '',
 alt: '',
 width: 468,
 height: 60,
 create: function(url, img, alt){
   this.url = url;
   this.img = img;
   this.alt = alt;
   return this;
 },

 display: function(ad){
   document.write('<center><a href="'+ this.url +'"><img src="'+ this.img
                 +'" border=2 alt="'+ this.alt  +'" title="'+ this.alt
                 +'" width='+ this.width +'468 height='+ this.height
                 +'></a><br/>');
 }
};

var hasrun;

function printad(){
  if(hasrun) return;
  var ads = new Array(Ad.create('http://www.e-classifieds.net',
                                '/banners/eclassbanner.gif',
                                'Classifieds For Every Web Site!'),
                      Ad.create('http://www.hagenhosting.com',
                                '/banners/banner.gif',
                                'Premium Quality Web Hosting!')
                     );
  var num = Math.floor(Math.random() * ads.length);
  ads[num].display();
  hasrun = 1;
}

printad();