function ifvuoto (strng, subj) {
var error="";
if (strng == "") {
   error = "\n The text field " + subj + " is empty.";
}
return error;    
}

function ifnonScelto (choice, subj) {
var error = "";
    if (choice == 0) {
    error = "\n Please choose " + subj + ".";
    }    
return error;
}   


function ifnonCheck (box, subj) {
var error = "";
    if (!box.checked) {
    error = "\n Non hai approvato " + subj + ".";
    }    
return error;
}