var NN3 = false;
image1alt = new Image();
image1alt.src = "img/egg_2nd_1.jpg";
image1alton = new Image();
image1alton.src = "img/egg_2nd_1.jpg";

image2alt = new Image();
image2alt.src = "img/egg_2nd_1.jpg";
image2alton = new Image();
image2alton.src = "img/egg_2.jpg";

image3alt = new Image();
image3alt.src = "img/egg_2nd_1.jpg";
image3alton = new Image();
image3alton.src = "img/egg_3.jpg";

image4alt = new Image();
image4alt.src = "img/egg_2nd_1.jpg";
image4alton = new Image();
image4alton.src = "img/egg_4.jpg";

function on4(name)   {
        document["altimg"].src = eval(name + "alton.src");
}
function off4(name)  {
        document["altimg"].src = eval(name + "alt.src");
}
NN3 = true;

function on(name)  {
        if (NN3) on4(name);
}
function off(name)  {
        if (NN3) off4(name);
}