var c = 1;

/* Preloading images */
var image1 = new Image();
image1.src = "a1.jpg";
var image2 = new Image();
image2.src = "a2.jpg";
var image3 = new Image();
image3.src = "a3.jpg";
var image4 = new Image();
image4.src = "a4.jpg";
var image5 = new Image();
image5.src = "a5.jpg";

function disp_img(w) {
    if (c == 6) {
        c = 1;
    }
    var img_src = "a" + c + ".jpg";
    document.ani.src = img_src;
    c++;
}
t = setInterval("disp_img(c)", 8000);