cornify_add = function() {
   var cornify_url = 'http://www.bullmanu.com/cornify/';
   var file = 'unicorn_';
   var count = 4;
   if (Math.random() > .7) {
      file = 'rainbow_';
      count = 7;
   }
   file += Math.ceil(Math.random()*count) + '.gif';
   var div = document.createElement('div');
   div.style.position = 'fixed';
   
   var height = Math.random()*.9;
   if (typeof(window.innerHeight) == 'number') {
      height = height*window.innerHeight+'px';
   } else if(document.documentElement && document.documentElement.clientHeight) {
      height = height*document.documentElement.clientHeight+'px';
   } else {
      height = height*100+'%'; 
   }
   
   div.style.top = height;
   div.style.left = Math.random()*90 + '%';
   var img = document.createElement('img');
   img.setAttribute('src',cornify_url+'immagini/'+file);
   var body = document.getElementsByTagName('body')[0];
   body.appendChild(div);
   div.appendChild(img);
}