numberOfImages = 29
randomImageNumber = (Math.floor(Math.random() * numberOfImages) + 1);
imageToLoad = "url('../../images/background_images/background_" + randomImageNumber + ".jpg')"
myCSS = "<style type='text/css' media='all'" + ">" + "<" + "!--body   {background-image: " + imageToLoad + "}--" + ">" + "<" + "/style>";
document.write(myCSS);