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

if (document.images) {
n_bh = newImage("http://www.e-scola.org/_estilos/casillaencima.gif");
}

function sh_item(where) {
if (document.images) {
storedLocation=where;
document.images["n"+where].src="http://www.e-scola.org/_estilos/casillaencima.gif"; 
}
}

function hd_item() {
if (document.images) {
where=storedLocation;
document.images["n"+where].src="http://www.e-scola.org/_estilos/casillavacia.gif"; 
}
}