//                    Rollover Script

        if (document.images) {            // Active Images
            img1on = new Image();
            img1on.src = "images/menu_home_on.gif";
            img1off = new Image();
            img1off.src = "images/menu_home.gif";
            img2on = new Image();
            img2on.src = "images/menu_story_on.gif";
            img2off = new Image();
            img2off.src = "images/menu_story.gif";
            img3on = new Image();
            img3on.src = "images/menu_mathematicians_on.gif";
            img3off = new Image();
            img3off.src = "images/menu_mathematicians.gif";
            img4on = new Image();
            img4on.src = "images/menu_glossary_on.gif";
            img4off = new Image();
            img4off.src = "images/menu_glossary.gif";
            img5on = new Image();
            img5on.src = "images/menu_sources_on.gif";
            img5off = new Image();
            img5off.src = "images/menu_sources.gif";
            img6on = new Image();
            img6on.src = "images/menu_contact_on.gif";
            img6off = new Image();
            img6off.src = "images/menu_contact.gif";
            }

// Function to 'activate' images.
function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "on.src");
        }
}
// Function to 'deactivate' images.
function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "off.src");
        }
}