if (document.images) 
{
    anim_img1 = new Image();
    anim_img1.src = "picts/anim_0.jpg";
    anim_img2 = new Image();
    anim_img2.src = "picts/anim_1.jpg";
    anim_img3 = new Image();
    anim_img3.src = "picts/anim_2.jpg";
    anim_img4 = new Image();
    anim_img4.src = "picts/anim_3.jpg";
}

function anim(nbr) 
{
    thetimer = setTimeout("anim_on_timeout('" +nbr+ "')", 300);
}

function anim_on_timeout(nbr) 
{
    if (document.images) 
    {
        if (nbr == "4") 
        {
            document["anim_img"].src = eval("anim_img4.src");
            anim('1');
        }
        else 
        {
            document["anim_img"].src = eval("anim_img" + nbr + ".src");
            anim(nbr = ++nbr);
        }
    }
}