function fromto(to){
    link = document.getElementById("to"+from);
    link.style.display = "";
    link = document.getElementById("to"+to);
    link.style.display = "none";

    elka = document.getElementById("tree");
    mainbg = document.getElementById("mainimg");

    if (logo = document.getElementById("logoso")) {
        logo.src = "f/so_" + to + ".png";
    }

    mainbg.style.backgroundImage = "url('f/bg-" + to + ".jpg')";
    document.body.style.backgroundImage = "url('f/bg-" + to + "-body.jpg')";

    if (to == 'night') {
        elka.style.display = "";
        document.body.style.backgroundColor = "#090a0a";
    } else {
        elka.style.display = "none";
        document.body.style.backgroundColor = "#d7dce2";
    }

    from = to;
}