if (document.images) {

    nav_01          = new Image(770, 9);
    nav_01.src      = "img/gui/nav/01.png";

    nav_02          = new Image(83, 20);
    nav_02.src      = "img/gui/nav/02.png";

    nav_03_on       = new Image(196, 38);
    nav_03_on.src   = "img/gui/nav/03h.png";
    nav_03_off      = new Image(196, 38);
    nav_03_off.src  = "img/gui/nav/03.png";

    nav_04_on      = new Image(209, 38);
    nav_04_on.src  = "img/gui/nav/04h.png";
    nav_04_off     = new Image(209, 38);
    nav_04_off.src = "img/gui/nav/04.png";

    nav_05_on      = new Image(199, 38);
    nav_05_on.src  = "img/gui/nav/05h.png";
    nav_05_off     = new Image(199, 38);
    nav_05_off.src = "img/gui/nav/05.png";

    nav_06          = new Image(83, 20);
    nav_06.src      = "img/gui/nav/06.png";

    nav_07_on      = new Image(83, 18);
    nav_07_on.src  = "img/gui/nav/07h.png";
    nav_07_off     = new Image(83, 18);
    nav_07_off.src = "img/gui/nav/07.png";

    nav_08_on      = new Image(83, 18);
    nav_08_on.src  = "img/gui/nav/08h.png";
    nav_08_off     = new Image(83, 18);
    nav_08_off.src = "img/gui/nav/08.png";

    nav_09_on      = new Image(83, 19);
    nav_09_on.src  = "img/gui/nav/09h.png";
    nav_09_off     = new Image(83, 19);
    nav_09_off.src = "img/gui/nav/09.png";

    nav_10_on      = new Image(196, 19);
    nav_10_on.src  = "img/gui/nav/10h.png";
    nav_10_off     = new Image(196, 19);
    nav_10_off.src = "img/gui/nav/10.png";

    nav_11_on      = new Image(209, 19);
    nav_11_on.src  = "img/gui/nav/11h.png";
    nav_11_off     = new Image(209, 19);
    nav_11_off.src = "img/gui/nav/11.png";

    nav_12_on      = new Image(199, 19);
    nav_12_on.src  = "img/gui/nav/12h.png";
    nav_12_off     = new Image(199, 19);
    nav_12_off.src = "img/gui/nav/12.png";

    nav_13_on      = new Image(83, 19);
    nav_13_on.src  = "img/gui/nav/13h.png";
    nav_13_off     = new Image(83, 19);
    nav_13_off.src = "img/gui/nav/13.png";

    nav_14         = new Image(83, 24);
    nav_14.src     = "img/gui/nav/14.png";

    nav_15_on      = new Image(196, 24);
    nav_15_on.src  = "img/gui/nav/15h.png";
    nav_15_off     = new Image(196, 24);
    nav_15_off.src = "img/gui/nav/15.png";

    nav_16_on      = new Image(209, 24);
    nav_16_on.src  = "img/gui/nav/16h.png";
    nav_16_off     = new Image(209, 24);
    nav_16_off.src = "img/gui/nav/16.png";

    nav_17_on      = new Image(199, 24);
    nav_17_on.src  = "img/gui/nav/17h.png";
    nav_17_off     = new Image(199, 24);
    nav_17_off.src = "img/gui/nav/17.png";

    nav_18         = new Image(83, 24);
    nav_18.src     = "img/gui/nav/18.png";

}

function imgOn(imgName) {
    if (document.images)
        document.images[imgName].src = eval(imgName + "_on.src");
}

function imgOff(imgName) {
    if (document.images)
        document.images[imgName].src = eval(imgName + "_off.src");
}