I have confused about the use of jquery ajax ,what's wrong with my code?

I just begin to learn jquery ajax framework here is my first attempt:

<div>
        <input id="ajax" type="button" value="Read" />
</div>

also the js code:

    $("#ajax").click(function () {
        $.ajax({
            type: "get",
            url: "http://www.111222333444555.com",
            //url: "http://www.google.com"
            //                    timeout: 2000,
            success: function () {
                alert("ajax success!");
            },
            error: function () {
                alert("ajax failed!");
            }
        });
    });

abviously the "http://www.111222333444555.com" is not accessible,so 开发者_如何学CI consider that resault is alert the "ajax failed!", but the resault is that the success function be executed,which alert "ajax success!"

then I change the url to "http://www.google.com",it alert "ajax success!" as well,

why the accessible url could cause the success function ?how can I escape the situation?I want when the url is not accessible,it will auto execute error function?How the $.ajax exactly works?

Please help me , thank you very much

Using the built-in objects, you cannot use Ajax to request a page that is outside of your page's domain.

There are solutions however...