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

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

var preloadFlag = false;

function preloadImagesIMG() {
        if (document.images) {
                x_01_over = newImageIMG("images/prism_on.gif");
                x_02_over = newImageIMG("images/testplate_on.gif");
                x_03_over = newImageIMG("images/coating_on.gif");
                x_04_over = newImageIMG("images/enpla_on.gif");
                x_05_over = newImageIMG("images/asphelical_on.gif");
                x_06_over = newImageIMG("images/injection_on.gif");
                x_07_over = newImageIMG("images/spherical_on.gif");
                x_08_over = newImageIMG("images/projector_on.gif");
                preloadFlag = true;
        }
}