if (document.images)
{
            img1on = new Image(); 
            img1on.src = "imagenes/boton01a.gif";  
            img1off = new Image(); 
            img1off.src ="imagenes/boton01.gif";                   
            
            img2on = new Image(); 
            img2on.src = "imagenes/boton02b.gif";  
            img2off = new Image(); 
            img2off.src ="imagenes/boton02.gif";          
            
            img3on = new Image(); 
            img3on.src = "imagenes/boton03c.gif";
            img3off = new Image(); 
            img3off.src ="imagenes/boton03.gif";            
            
            img4on = new Image(); 
            img4on.src ="imagenes/boton04d.gif";  
            img4off = new Image(); 
            img4off.src ="imagenes/boton04.gif";                      
                
            img5on = new Image(); 
            img5on.src ="imagenes/boton05e.gif";
            img5off = new Image(); 
            img5off.src ="imagenes/boton05.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");
}
}