if (document.images) {            // Active Images
            img1on = new Image();
            img1on.src = "images/welcome_ovr.gif"; 
            img2on = new Image(); 
            img2on.src = "images/who_ovr.gif";  
            img3on = new Image();
            img3on.src = "images/medicine_ovr.gif";
            img4on = new Image();
            img4on.src = "images/products_ovr.gif";
           img5on = new Image();
            img5on.src = "images/news_ovr.gif";
           img6on = new Image();
            img6on.src = "images/contact_ovr.gif";
           img7on = new Image();
            img7on.src = "images/trade_ovr.gif";

            img1off = new Image(); 
            img1off.src = "images/welcome.gif"; 
            img2off = new Image();
            img2off.src = "images/who.gif"; 
            img3off = new Image();
            img3off.src = "images/medicine.gif";
            img4off = new Image();
            img4off.src = "images/products.gif";
            img5off = new Image();
            img5off.src = "images/news.gif";
            img6off = new Image();
            img6off.src = "images/contact.gif";
            img7off = new Image();
            img7off.src = "images/trade.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");
        }
}