function cambia(id, over) {
    document.getElementById(id).className = (over ? 'block_ns_over' : 'block_ns');
}

function apri(link) {
    document.location.href = link;
}

pic1= new Image(170,27); 
pic1.src="img/block_ns_out.gif";
pic2= new Image(170,27); 
pic2.src="img/block_ns_over.gif";