if (document.images) {            // Active Images
            img1on = new Image();      
            img1on.src = "imagenes/menu_master_1_over.gif"; 
            img2on = new Image();      
            img2on.src = "imagenes/menu_master_2_over.gif"; 
            img3on = new Image();      
            img3on.src = "imagenes/menu_master_3_over.gif";
            img4on = new Image();      
            img4on.src = "imagenes/menu_master_4_over.gif";
            img5on = new Image();      
            img5on.src = "imagenes/menu_master_5_over.gif";
            img6on = new Image();      
            img6on.src = "imagenes/menu_master_6_over.gif";
            img7on = new Image();      
            img7on.src = "imagenes/menu_master_7_over.gif";
            img8on = new Image();      
            img8on.src = "imagenes/menu_master_8_over.gif";
            img9on = new Image();      
            img9on.src = "imagenes/menu_master_9_over.gif";
            img10on = new Image();      
            img10on.src = "imagenes/menu_master_10_over.gif";
                                                
            img1off = new Image();      
            img1off.src = "imagenes/menu_master_1_off.gif"; 
            img2off = new Image();      
            img2off.src = "imagenes/menu_master_2_off.gif"; 
            img3off = new Image();      
            img3off.src = "imagenes/menu_master_3_off.gif"; 
            img4off = new Image();      
            img4off.src = "imagenes/menu_master_4_off.gif"; 
            img5off = new Image();      
            img5off.src = "imagenes/menu_master_5_off.gif"; 
            img6off = new Image();      
            img6off.src = "imagenes/menu_master_6_off.gif"; 
            img7off = new Image();      
            img7off.src = "imagenes/menu_master_7_off.gif"; 
            img8off = new Image();      
            img8off.src = "imagenes/menu_master_8_off.gif"; 
            img9off = new Image();      
            img9off.src = "imagenes/menu_master_9_off.gif"; 
            img10off = new Image();      
            img10off.src = "imagenes/menu_master_10_off.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");
        }
}