function banner() { 
}; 
banner = new banner(); 
number = 0; 
banner[number++] = "<a href='adclick.php?banner_id=1' target='_blank'><img src='http://www.trekkingthai.com/pic1/bannere.gif' width='340' height='60' border='0'></a>";
increment = Math.floor(Math.random() * number); 
document.write(banner[increment]);