if (document.images) {
            img1on = new Image();      
            img1on.src = "images/bt2/hd4a1-off.gif";      
			img2on = new Image();      
            img2on.src = "images/bt2/hd4b1-off.gif";  
			img3on = new Image();      
            img3on.src = "images/bt2/hd4c1-off.gif";  
			img4on = new Image();      
            img4on.src = "images/bt2/hd4d1-off.gif";
			img5on = new Image();      
            img5on.src = "images/bt2/hd4e1-off.gif";
			img6on = new Image();      
            img6on.src = "images/bt2/hd4f1-off.gif";
			img7on = new Image();      
            img7on.src = "images/bt2/hd4g1-off.gif";



            img1off = new Image();      
            img1off.src = "images/bt2/hd4a1-on.gif";      
			img2off = new Image();      
            img2off.src = "images/bt2/hd4b1-on.gif";  
			img3off = new Image();      
            img3off.src = "images/bt2/hd4c1-on.gif";  
			img4off = new Image();      
            img4off.src = "images/bt2/hd4d1-on.gif";  
			img5off = new Image();      
            img5off.src = "images/bt2/hd4e1-on.gif";  
			img6off = new Image();      
            img6off.src = "images/bt2/hd4f1-on.gif";  
			img7off = new Image();      
            img7off.src = "images/bt2/hd4g1-on.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");
        }
}