Jquery :: JS Focus Doesn't Work?

$("#username").bind('blur',function(){
val = $(this).val();
if(val == ""){
alert("Username is a required field, please fill it in!");
$("#username-div").css("background-color", "#eeccdd");
$("#username-error").html("Please fill this");
$(this).focus();
}
});

this code doesnt seem to focus. i have also tried Javascript and even that isnt working? Basically i would like that input box with id username to be focused if user leaves it empty and moves to next form field?