if (document.images) {
                  
            img1on = new Image(); 
            img1on.src = "bot1b.gif";   
            img1off = new Image(); 
            img1off.src = "bot1a.gif"; 
                  
            img2on = new Image(); 
            img2on.src = "bot2b.gif";   
            img2off = new Image(); 
            img2off.src = "bot2a.gif"; 
                  
            img3on = new Image(); 
            img3on.src = "bot3b.gif";   
            img3off = new Image(); 
            img3off.src = "bot3a.gif"; 
                  
            img4on = new Image(); 
            img4on.src = "bot4b.gif";   
            img4off = new Image(); 
            img4off.src = "bot4a.gif"; 

            img5on = new Image(); 
            img5on.src = "bot5a.gif";   
            img5off = new Image(); 
            img5off.src = "bot5a.gif"; 

            img6on = new Image(); 
            img6on.src = "bot6a.gif";   
            img6off = new Image(); 
            img6off.src = "bot6a.gif"; 
       }


function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "on.src");
        }
}


function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "off.src");
        }
}