if (document.images) {
            img01on = new Image();          
            img01on.src = "images/btn01-on.gif";   
            img02on = new Image();          
            img02on.src = "images/btn02-on.gif";     		
            img03on = new Image();          
            img03on.src = "images/btn03-on.gif";    
            img04on = new Image();          
            img04on.src = "images/btn04-on.gif";    
            img05on = new Image();          
            img05on.src = "images/btn05-on.gif";
			  
            img01off = new Image();          
            img01off.src = "images/btn01-off.gif"; 
            img02off = new Image();          
            img02off.src = "images/btn02-off.gif";     		
            img03off = new Image();          
            img03off.src = "images/btn03-off.gif";    
            img04off = new Image();          
            img04off.src = "images/btn04-off.gif";    
            img05off = new Image();          
            img05off.src = "images/btn05-off.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");
        }
}