$("#login").click(function(){
if($("#username").val().length > 0 && $("#password").val().length > 0){
                    $.ajax({
                url:"login.php",
                data:{username:$("#username").val(),password:$("#password").val()},
                type:"POST",
                success: function(data){
                if(data == "ok") window.location = "success.php";
                else $("#slfErrorAlert").html(data).show();
                }
                });
}
else {
$("#slfErrorAlert").html("Username and password is required").show();
}
    return false
    });