img = new Array();
img[0] = "images/catchimg/catch-img-00.jpg";
img[1] = "images/catchimg/catch-img-01.jpg";
img[2] = "images/catchimg/catch-img-02.jpg";
img[3] = "images/catchimg/catch-img-03.jpg";
n = Math.floor(Math.random()*img.length);