if (document.images) {

    img1_2on = new Image();
    img1_2on.src = "./img/umisho_top_but_outline_on.gif";
    img1_3on = new Image();
    img1_3on.src = "./img/umisho_top_but_cast_on.gif";
    img1_4on = new Image();
    img1_4on.src = "./img/umisho_top_but_q_a_on.gif";


    img1_2off = new Image();
    img1_2off.src = "./img/umisho_top_but_outline.gif";
    img1_3off = new Image();
    img1_3off.src = "./img/umisho_top_but_cast.gif";
    img1_4off = new Image();
    img1_4off.src = "./img/umisho_top_but_q_a.gif";

}

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

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