function stringFilter(s){
filteredValues = "abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
var i;
var returnString = "";
for (i = 0; i < s.length; i++) {
var c = s.charAt(i);
if (filteredValues.indexOf(c) != -1) returnString += c;
}
document.getElementById("userName").value = returnString;
}