function newImage(arg) {
if (document.images) {
rslt = new Image();
rslt.src = arg;
return rslt;
}
}

if (document.images) {
n1_h = newImage("images/n1_h.gif");
n2_h = newImage("images/n2_h.gif");
n3_h = newImage("images/n3_h.gif");
n4_h = newImage("images/n4_h.gif");
n5_h = newImage("images/n5_h.gif");
n6_h = newImage("images/n6_h.gif");
}

function sh(where) {
if (document.images) {
storedLocation=where;
document.images[where].src="images/"+where+"_h.gif"; 
}
}

function hd() {
if (document.images) {
where=storedLocation;
document.images[where].src="images/"+where+".gif"; 
}
}