function chatbar() {
if (document.getElementById('chatbutton').innerHTML == "Apri") {
document.getElementById('cboxdiv').style.visibility = 'visible';
document.getElementById('chatbutton').innerHTML = 'Chiudi';
}
else {
document.getElementById('cboxdiv').style.visibility = 'hidden';
document.getElementById('chatbutton').innerHTML = 'Apri';
}
}