function banner() {
    var banner =  new Array("banner001.png","banner002.png","banner003.png","banner999.png");
    var path = document.getElementsByTagName('script')[0].src;
    path = path.slice(0, path.length-9)+"banner/";
    var x =  Math.floor((Math.random() * banner.length));
    path = path+banner[x];
    document.getElementById('banner').src = path;
}