// JavaScript Document
window.onload = function () {
    var header = document.getElementById('banieres');
    var pictures = new Array('banieres/image1.jpg','banieres/image2.jpg','banieres/image3.jpg','banieres/image4.jpg','banieres/image5.jpg','banieres/image6.jpg','banieres/image7.jpg','banieres/image8.jpg','banieres/image9.jpg','banieres/image10.jpg' ,'banieres/image11.jpg', 'banieres/image12.jpg','banieres/image13.jpg');
    var numPics = pictures.length;
    if (document.images) {
        var chosenPic = Math.floor((Math.random() * numPics));
        header.style.background = 'url(' + pictures[chosenPic] + ')';
    }
}