function newImage(arg) {
    if (document.images) {
        rslt = new Image();
        rslt.src = arg;
        return rslt;
    }
}

function changeImages() {
    if (document.images && (preloadFlag == true)) {
        for (var i=0; i<changeImages.arguments.length; i+=2) {
            document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
        }
    }
}

var preloadFlag = false;
function preloadImages() {
    if (document.images) {
        nav_loaedition_over = newImage("images/nav-loaedition-over.gif");
        nav_life_over = newImage("images/nav-life-over.gif");
        nav_work_over = newImage("images/nav-work-over.gif");
        nav_commentary_over = newImage("images/nav-commentary-over.gif");
        nav_loalogo_over = newImage("images/nav-loalogo-over.gif");
        preloadFlag = true;
    }
}