var state = 'none'; 

function showhide(layer_ref) { 
if (state == 'block') { 
state = 'none'; 
} 
else { 
state = 'block'; 
} 
if (document.all) { //IS IE 4 or 5 (or 6 beta) 
eval( "document.all." + layer_ref + ".style.display = state"); 
} 
if (document.layers) { //IS NETSCAPE 4 or below 
document.layers[layer_ref].display = state; 
} 
if (document.getElementById &&!document.all) { 
hza = document.getElementById(layer_ref); 
hza.style.display = state; 
} 
} 
function add(id){
var obj = document.getElementById(id);
 obj.src = obj.src.replace(".jpg","-over.jpg"); 
 obj.src = obj.src.replace(".png","-over.png"); 
}
function remove(id){
 var obj = document.getElementById(id);
 var img = obj.src;
 obj.src = img.replace("-over",""); 
}