provato :
codice:
window.onload=function titolos(){
var CountDefault = document.getElementsByTagName("titolo")[0].value;
document.getElementById('charCount').innerHTML = (50-CountDefault);
}

oppure

window.onload=function (){
var CountDefault = document.getElementsByTagName("titolo")[0].value;
document.getElementById('charCount').innerHTML = (50-CountDefault);
}

oppure

window.onload=function (){
var CountDefault = document.getElementsByTagName("titolo")[0].value
document.getElementById('charCount').innerHTML = (50-CountDefault)
}
Ma nn funge.....