jQuery $ .ajax（）响应非常慢

In my webpage (questions.php), I used a button, when a user click on it $.ajax() loads a form for user to ask question. This form is a separate page (ask_question_form.php). I used the following jquery code.

$(document).ready(function(e) {
    $("#ask_new_question").click(function(){
    $.ajax({url:"./ask_question_form.php",success:function(result){
        $("#question_result_box").slideToggle(100,function(){
        $("#question_result").html(result)});
    }});
    });
});

When user click on button (with id=ask_new_quetion) $.ajax() loads the for to div (with id=question_result). Now the problem is when the page loads and i click on the button for the first time, it takes at least 15 seconds to response... After that the response approximately takes 7 to 10 second.. Is there any way to speed up this response time?? I have tested it on IE, firefox and chrome... gives the same result...