$(document).ready(function() {
$("#username").change(function() {
var usr = $("#username").val();
if (usr.length >= 3) {
$("#status").html(' 
Checking availability...');
$.ajax({
type: "POST",
url: "/includes/username_validation.php",
data: "username=" + usr,
success: function(msg) {
$("#status").ajaxComplete(function(event, request, settings) {
if (msg == 'TRUE') {
$("#username_label").removeClass('Errors');
$(this).html(' 
Username is available!');
} else {
$("#username_label").addClass('Errors');
$(this).html(' 
That username is unavailable');
}
});
}
});
} else {
$("#status").html(' At least 4 characters are required.');
$("#username").removeClass('object_ok'); // if necessary
//$("#username").addClass("object_error");
}
});
});